Prevent callback from being called after control is disposed. Fixes #1317.
Add BackgroundFetch plugin in order to allow perioding fetching of all remotes automatically.
Implement logic to skip fetching updates when git.exe is already running.
Merge with latest master.
Run git asynchronously so that the UI is not frozen.
Promote IsRunningGitProcess() method to IGitModule interface.
Ensure the background fetching is done on a worker thread so as to not block the UI.
Ensure plugins are given a chance to unload when the app is closed.
Add Rx as NuGet packages to the solutions.
Switch back from using RunGitCmdAsync to using GitCommand.
Add command to preinstall nuget packages on build script.
EnableNuGetPackageRestore in build.cmd
Refresh view after fetch
Merge remote-tracking branch 'gitextensions/master' into BuildServerIntegration-plugin

Conflicts:
	GitExtensions.VS2012.sln
	Setup/BuildInstallers.VS2012.cmd
	Setup/BuildInstallers.cmd
	Setup/Product.wxs
Merge branch 'BuildServerIntegration-plugin' into all

Conflicts:
	Plugins/BackgroundFetch/BackgroundFetchPlugin.cs