PBGitRepository: ensure to have workingDirectory in -initWithURL: to fix crashes in PBGitCommitController.

I had these crashes only when opening Submodules, didn't try to find why though.
PBGitRepository: add explicit module detection in -workingDirectory.
Fix leaks in gitx_askpasswd_main.m
Fix leaks in gitx.m
Fix leaks and warnings in GitX
Use standard compare for the sidebar elements.

That way tags for version 1.0.10 will be sorted after 1.0.9 and not
after 1.0.1.
Fixing broken URLs.
Fixing zombie.
Project touched by Xcode 4.6.
Merge commit 'da7a10f6e0d46d139ca1a8b37c73ff8b39c5bfe2'
Touching “PBGitHistoryView.xib” with Xcode 4.6.2.
Changing divider style in “PBGitHistoryView.xib” to “thick”.
Fixing zombie that prevented “Stash local changes...” from working.
Fixing deprecation.
Cleanup.
Replacing deprecated “-compositeToPoint:operation:”.
Rewriting icon placement code to be semantic and thus more readable.