Add support for additional edge cases to RuleLinkExpander.

* Add support for rules with capital letters, such as Fileset
* Add support for static page headings with periods.
* Run the expander on the HTML doc for the name attribute.
* Add functions to initial rule index.

--
MOS_MIGRATED_REVID=115925884
diff --git a/src/main/java/com/google/devtools/build/docgen/DocgenConsts.java b/src/main/java/com/google/devtools/build/docgen/DocgenConsts.java
index d50a299..da7a1da 100644
--- a/src/main/java/com/google/devtools/build/docgen/DocgenConsts.java
+++ b/src/main/java/com/google/devtools/build/docgen/DocgenConsts.java
@@ -100,7 +100,7 @@
    * (e.g. common-definitions.label-expansion).
    */
   public static final Pattern BLAZE_RULE_LINK = Pattern.compile(
-      "\\$\\{link (([a-z_-]+)(\\.([a-z_-]+))?)\\}");
+      "\\$\\{link (([a-zA-Z_-]+)(\\.([a-zA-Z_\\.-]+))?)\\}");
 
   /**
    * i.e. <!-- #BLAZE_RULE(NAME = RULE_NAME, TYPE = RULE_TYPE, FAMILY = RULE_FAMILY) -->