[FAB-8411] peer logging CLI documentation

This CR adds documentation for the `peer logging` CLI commands.

Change-Id: Ibfd47aed74a28855892a2f64515241251c83a4d6
Signed-off-by: Will Lahti <wtlahti@us.ibm.com>

Author: wlahti

docs/source/commands/peerlogging.md

@@ -0,0 +1,132 @@
+# peer logging
+## Description
+
+The `peer logging` subcommand allows administrators to dynamically view and
+configure the log levels of a peer.
+
+## Syntax
+
+The `peer logging` subcommand has the following syntax:
+
+```
+peer logging getlevel
+peer logging setlevel
+peer logging revertlevels
+```
+
+The different subcommand options (getlevel, setlevel, and revertlevels) relate
+to the different logging operations that are relevant to a peer.
+
+Each peer logging subcommand is described together with its options in its own
+section in this topic.
+
+## peer logging getlevel
+
+### Get Level Description
+
+The `peer logging getlevel` command allows administrators to get the current
+level for a logging module.
+
+### Get Level Syntax
+
+The `peer logging getlevel` command has the following syntax:
+
+```
+peer logging getlevel <module-name>
+```
+
+### Get Level Flags
+
+The `peer logging getlevel` command does not have any command-specific flags.
+
+### Get Level Usage
+
+Here is an example of the `peer logging getlevel` command:
+
+  * To get the log level for module `peer`:
+
+    ```
+    peer logging getlevel peer
+
+    2018-02-22 19:10:08.633 UTC [cli/logging] getLevel -> INFO 001 Current log level for peer module 'peer': DEBUG
+    2018-02-22 19:10:08.633 UTC [main] main -> INFO 002 Exiting.....
+
+    ```
+
+## peer logging setlevel
+
+### Set Level Description
+
+The `peer logging setlevel` command allows administrators to set the current
+level for all logging modules that match the module name regular expression
+provided.
+
+### Set Level Syntax
+
+The `peer logging setlevel` command has the following syntax:
+
+```
+peer logging setlevel <module-name-regular-expression> <log-level>
+```
+
+### Set Level Flags
+
+The `peer logging setlevel` command does not have any command-specific flags.
+
+### Set Level Usage
+
+Here are some examples of the `peer logging setlevel` command:
+
+  * To set the log level for modules matching the regular expression `peer` to
+    log level `WARNING`:
+
+    ```
+    peer logging setlevel peer warning
+    2018-02-22 19:14:51.217 UTC [cli/logging] setLevel -> INFO 001 Log level set for peer modules matching regular expression 'peer': WARNING
+    2018-02-22 19:14:51.217 UTC [main] main -> INFO 002 Exiting.....
+
+    ```
+
+  * To set the log level for modules that match the regular expression `^gossip`
+    (i.e. all of the `gossip` logging submodules of the form
+    `gossip/<submodule>`) to log level `ERROR`:
+
+    ```
+    peer logging setlevel ^gossip error
+
+    2018-02-22 19:16:46.272 UTC [cli/logging] setLevel -> INFO 001 Log level set for peer modules matching regular expression '^gossip': ERROR
+    2018-02-22 19:16:46.272 UTC [main] main -> INFO 002 Exiting.....
+    ```
+
+## peer logging revertlevels
+
+### Revert Levels Description
+
+The `peer logging revertlevels` command allows administrators to revert the
+log levels of all modules to their level at the time the peer completed its
+startup process.
+
+### Revert Levels Syntax
+
+The `peer logging revertlevels` command has the following syntax:
+
+```
+peer logging revertlevels
+```
+
+### Revert Levels Flags
+
+The `peer logging revertlevels` command does not have any command-specific
+flags.
+
+### Revert Levels Usage
+
+Here is an example of the `peer logging revertlevels` command:
+
+  * ```
+    peer logging revertlevels
+
+    2018-02-22 19:18:38.428 UTC [cli/logging] revertLevels -> INFO 001 Log levels reverted to the levels at the end of peer startup.
+    2018-02-22 19:18:38.428 UTC [main] main -> INFO 002 Exiting.....
+
+    ```