Remove shortcut from SVN commands

This is to free up the shortcut for use in TextMate proper as these aren't commonly used commands.
Cleanup menu

Titlecase 'Add File to the Index' and move it and 'Amend Last Commit…' in the menu.
Add to Index now prefer selection in file browser

If there is no selection, it’ll add the current file to the index.
Add description key (shows in bundles window)

"Support for the Git version control system"
merge