Update documentation of gitiles.config

The gitiles.config file is primarily used to configure the behavior
of the core gitiles servlet, and is only used (so far) for a single
configuration of the plugin. Update the documentation to make this a
bit clearer.

Change-Id: Ife5e7901655fe3df3298978ea2b60aad4ff9296f

src/main/resources/+Documentation/config.md

diff --git a/src/main/resources/+Documentation/config.md b/src/main/resources/+Documentation/config.md
index 40a137f..c5e9b54 100644
--- a/src/main/resources/+Documentation/config.md
+++ b/src/main/resources/+Documentation/config.md
@@ -23,11 +23,14 @@
 by SHA-1 if they are reachable from a visible branch.
 
 File `gitiles.config`
--------------------------
+---------------------
 
-The optional file `$site_path/etc/gitiles.config` is a Git-style config file 
-that controls the settings for the gitiles plugin.  The name of the link appears
-in Gerrit can be configured under `gerrit.linkname`.
+The optional file `$site_path/etc/gitiles.config` is a Git-style config file
+that controls the settings for the core gitiles servlet. Some settings specific
+to the gitiles plugin can also be configured.
+
+The name of the link that appears in Gerrit can be configured with
+`gerrit.linkname`.
 
 ```
   [gerrit]