rpc: Argument name consistency

The meaning is clear from the context, and we're inconsistent here.
Also save typing when using named arguments.

- `bitcoinaddress` -> `address`
- `bitcoinprivkey` -> `privkey`
- `bitcoinpubkey` -> `pubkey`

src/rpc/blockchain.cpp

@@ -875,7 +875,7 @@ UniValue gettxout(const JSONRPCRequest& request)
             "     \"reqSigs\" : n,          (numeric) Number of required signatures\n"
             "     \"type\" : \"pubkeyhash\", (string) The type, eg pubkeyhash\n"
             "     \"addresses\" : [          (array of string) array of bitcoin addresses\n"
-            "        \"bitcoinaddress\"     (string) bitcoin address\n"
+            "        \"address\"     (string) bitcoin address\n"
             "        ,...\n"
             "     ]\n"
             "  },\n"

src/rpc/misc.cpp

@@ -152,14 +152,14 @@ UniValue validateaddress(const JSONRPCRequest& request)
 {
     if (request.fHelp || request.params.size() != 1)
         throw runtime_error(
-            "validateaddress \"bitcoinaddress\"\n"
+            "validateaddress \"address\"\n"
             "\nReturn information about the given bitcoin address.\n"
             "\nArguments:\n"
-            "1. \"bitcoinaddress\"     (string, required) The bitcoin address to validate\n"
+            "1. \"address\"     (string, required) The bitcoin address to validate\n"
             "\nResult:\n"
             "{\n"
             "  \"isvalid\" : true|false,       (boolean) If the address is valid or not. If not, this is the only property returned.\n"
-            "  \"address\" : \"bitcoinaddress\", (string) The bitcoin address validated\n"
+            "  \"address\" : \"address\", (string) The bitcoin address validated\n"
             "  \"scriptPubKey\" : \"hex\",       (string) The hex encoded scriptPubKey generated by the address\n"
             "  \"ismine\" : true|false,        (boolean) If the address is yours or not\n"
             "  \"iswatchonly\" : true|false,   (boolean) If the address is watchonly\n"
@@ -325,10 +325,10 @@ UniValue verifymessage(const JSONRPCRequest& request)
 {
     if (request.fHelp || request.params.size() != 3)
         throw runtime_error(
-            "verifymessage \"bitcoinaddress\" \"signature\" \"message\"\n"
+            "verifymessage \"address\" \"signature\" \"message\"\n"
             "\nVerify a signed message\n"
             "\nArguments:\n"
-            "1. \"bitcoinaddress\"  (string, required) The bitcoin address to use for the signature.\n"
+            "1. \"address\"  (string, required) The bitcoin address to use for the signature.\n"
             "2. \"signature\"       (string, required) The signature provided by the signer in base 64 encoding (see signmessage).\n"
             "3. \"message\"         (string, required) The message that was signed.\n"
             "\nResult:\n"
@@ -508,9 +508,9 @@ static const CRPCCommand commands[] =
   //  --------------------- ------------------------  -----------------------  ----------
     { "control",            "getinfo",                &getinfo,                true,  {} }, /* uses wallet if enabled */
     { "control",            "getmemoryinfo",          &getmemoryinfo,          true,  {} },
-    { "util",               "validateaddress",        &validateaddress,        true,  {"bitcoinaddress"} }, /* uses wallet if enabled */
+    { "util",               "validateaddress",        &validateaddress,        true,  {"address"} }, /* uses wallet if enabled */
     { "util",               "createmultisig",         &createmultisig,         true,  {"nrequired","keys"} },
-    { "util",               "verifymessage",          &verifymessage,          true,  {"bitcoinaddress","signature","message"} },
+    { "util",               "verifymessage",          &verifymessage,          true,  {"address","signature","message"} },
     { "util",               "signmessagewithprivkey", &signmessagewithprivkey, true,  {"privkey","message"} },
 
     /* Not shown in help */

src/rpc/rawtransaction.cpp

@@ -174,7 +174,7 @@ UniValue getrawtransaction(const JSONRPCRequest& request)
             "         \"reqSigs\" : n,            (numeric) The required sigs\n"
             "         \"type\" : \"pubkeyhash\",  (string) The type, eg 'pubkeyhash'\n"
             "         \"addresses\" : [           (json array of string)\n"
-            "           \"bitcoinaddress\"        (string) bitcoin address\n"
+            "           \"address\"        (string) bitcoin address\n"
             "           ,...\n"
             "         ]\n"
             "       }\n"

src/wallet/rpcdump.cpp

@@ -520,11 +520,11 @@ UniValue dumpprivkey(const JSONRPCRequest& request)
 
     if (request.fHelp || request.params.size() != 1)
         throw runtime_error(
-            "dumpprivkey \"bitcoinaddress\"\n"
-            "\nReveals the private key corresponding to 'bitcoinaddress'.\n"
+            "dumpprivkey \"address\"\n"
+            "\nReveals the private key corresponding to 'address'.\n"
             "Then the importprivkey can be used with this output\n"
             "\nArguments:\n"
-            "1. \"bitcoinaddress\"   (string, required) The bitcoin address for the private key\n"
+            "1. \"address\"   (string, required) The bitcoin address for the private key\n"
             "\nResult:\n"
             "\"key\"                (string) The private key\n"
             "\nExamples:\n"