Merge pull request #9517 from terminalmage/docs

Add note about ubuntu 12.04 not having sufficient GitPython for gitfs
Fix sphinx warning due to mismatched header lines
clarify that file_recv is a master config option
Normalize line length
Fix sphinx build errors/warnings
Fix hyperlinks in hydrogen release notes
Merge pull request #9521 from terminalmage/sphinx

Fix various docs build errors and warnings
Add some links to the fileserver backends docs

This commit turns some of the config file parameters into links to the
master config file docs, and also links to the pages for the fileserver
backends being described as well.