Tidy up documentation of the /config REST API endpoint

Fix minor grammatical issues.

Make the style of the documentation consistent with the other
existing documentation.

Change-Id: Ia238fd12726d05a8580d1f09257ebf2f26f75eab
diff --git a/Documentation/rest-api-config.txt b/Documentation/rest-api-config.txt
index 65e18a7..0250e26 100644
--- a/Documentation/rest-api-config.txt
+++ b/Documentation/rest-api-config.txt
@@ -15,12 +15,13 @@
 [verse]
 'GET /config/server/capabilities'
 
-Lists the capabilities that are available in system. There are two kinds of
-capabilities: core and plugin-owned capabilities.
+Lists the capabilities that are available in the system. There are two
+kinds of capabilities: core and plugin-owned capabilities.
 
-As result a map is returned that maps the capability names to
-capability descriptions. The entries in the map are sorted
-by capability name.
+As result a map of link:#capability-info[CapabilityInfo] entities is
+returned.
+
+The entries in the map are sorted by capability ID.
 
 .Request
 ----
@@ -117,6 +118,19 @@
   }
 ----
 
+[[capability-info]]
+CapabilityInfo
+~~~~~~~~~~~~~~
+The `CapabilityeInfo` entity contains information about a capability.
+
+[options="header",width="50%",cols="1,5"]
+|=================================
+|Field Name           |Description
+|`kind`               |`gerritcodereview#capability`
+|`id`                 |capability ID
+|`name`               |capability name
+|=================================
+
 
 GERRIT
 ------