Submodule GitExtensionsDoc updated

Submodule GitExtensionsDoc:
    > a120c4e - Fix incomplete sentence.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of git://github.com/gitextensions/gitextensions
Merge branch 'master' of git://github.com/gitextensions/gitextensions
Merge branch 'master' of git://github.com/gitextensions/gitextensions
Merge branch 'master' of git://github.com/gitextensions/gitextensions
Merge branch 'master' of https://github.com/gitextensions/gitextensions
Merge branch 'master' of git://github.com/vbjay/gitextensions
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Add submodule fetch option to BackgroundFetch plugin
Add Fetch All Submodules sample script
Update Korean translation (Settings)
Support VS2013 build
Update Korean translation (Settings)
Update Korean translation (Patch & Settings)
Merge branch 'translate_korean' of github.com:mrahn80/gitextensions into translate_korean
Truncate long filenames: Option to display file name only
Include Git.hub.dll as required