Add logo to RTD and release # to TOC

- added favicon - file gitextensions/bin/logo/git-extensions-logo-final-32.png converted to .ico
- added logo - file gitextensions/bin/logo/git-extensions-logo-final-128.png
- add release number to title on TOC page
Merge pull request #36 from rthorp/fix/Add_logo

Add logo to RTD and release # to TOC