window: set back button arrow icon according to locale's text direction

https://bugzilla.gnome.org/show_bug.cgi?id=707211
Add an AppData description for gitg
User Information dialog is now Author Details

Convert User Information dialog into a template
Rename all 'User Information' functions to 'Author Details'
Add "Get Patch" button to Diff View
Turn off WebKit caching

Apply kov's suggestions to try to keep WebKit mem usage under control.
It does not seem to help here, but that may be due to my old WK...
Anyway I do not think we want caching, so let's turn it off.
Updated POTFILES.in and POTFILES.skip
Updated Polish translation
Updated Slovenian translation
Updated Czech translation
[l10n] Updated Italian translation.
Updated Lithuanian translation
Updated Brazilian Portuguese translation proofread by Rafael Ferreira
Fix 'Clone Repository' dialog errors

Route 'Clone Repository' dialog errors to new GtkInfobar.