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
Merge branch 'pr/n2056_vbjay'

Conflicts:
	Plugins/BackgroundFetch/BackgroundFetchPlugin.cs