Submodule GitExtensionsDoc updated

Submodule GitExtensionsDoc:
    > a120c4e - Fix incomplete sentence.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Plugin to create pull request for repository hosted in Atlassian Stash.
Implement source/target repo selection.
Add gimmicks
Bug fix
- Add project to Visual Studio 2012 solution

- Fix reference to Newtonsoft.Json (use the same version that Gerrit plugin use)
- Add the Stash.dll into the installer project
Change to target .NET framework 4.0 Client Profile
Rewrite the rest requests using Restsharp
Minor bug fix
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