Fix missing ] and link help in.

This unbreaks building man pages.
Fix name of top level geogit man page.
Fix header lengths

Short header underlines cause warnings from sphinx. Long ones probably will at some point...
Fix docs for osmapplydiff - minor rewording and header length
Fix sl/pg cut-n-paste and make minor cleanups ind ocs.
Merge pull request #639 from bradh/docs_2014_03_21

Docs 2014 03 21