schema: Move schema.json -> config-schema.json and similar

To make it clear that these schemas are for validating config.json
(and not, for example, state JSON).  I've left the IDs alone for now,
because my PR adjusting those was rejected [1].

The rule for the -schema portion is "use it for entrypoint files" [2].

[1]: opencontainers#453
[2]: opencontainers#481 (comment)

Signed-off-by: W. Trevor King <wking@tremily.us>

schema/README.md

@@ -2,22 +2,22 @@
 
 ## Overview
 
-This directory contains the [JSON Schema](http://json-schema.org/) for
-validating the `config.json` of this container runtime specification.
+This directory contains the [JSON Schema](http://json-schema.org/) for validating JSON covered by this specification.
 
 The layout of the files is as follows:
-* [schema.json](schema.json) - the primary entrypoint for the whole schema document
-* [schema-linux.json](schema-linux.json) - this schema is for the Linux-specific sub-structure
-* [schema-solaris.json](schema-solaris.json) - this schema is for the Solaris-specific sub-structure
+
+* [config-schema.json](config.json) - the primary entrypoint for the [configuration](../config.md) schema
+* [config-linux.json](config-linux.json) - the [Linux-specific configuration sub-structure](../config-linux.md)
+* [config-solaris.json](config-solaris.json) - the [Solaris-specific configuration sub-structure](../config-solaris.md)
 * [defs.json](defs.json) - definitions for general types
 * [defs-linux.json](defs-linux.json) - definitions for Linux-specific types
 * [validate.go](validate.go) - validation utility source code
 
 
 ## Utility
 
-There is also included a simple utility for facilitating validation of a
-`config.json`. To build it:
+There is also included a simple utility for facilitating validation.
+To build it:
 
 ```bash
 export GOPATH=`mktemp -d`
@@ -35,5 +35,5 @@ make validate
 Then use it like:
 
 ```bash
-./validate schema.json <yourpath>/config.json
+./validate config-schema.json <yourpath>/config.json
 ```

schema/schema.json → schema/config-schema.json

@@ -166,10 +166,10 @@
             }
         },
         "linux": {
-            "$ref": "schema-linux.json#/linux"
+            "$ref": "config-linux.json#/linux"
         },
         "solaris": {
-            "$ref": "schema-solaris.json#/solaris"
+            "$ref": "config-solaris.json#/solaris"
         }
     },
     "required": [