Bump xwt to match what md-addins is using
[T4] Fix CompilerError ctor args in base template

Tested to match VS T4 engine.

BXC21691 - T4 null-reference usage for fileName when creating a
CompilerError object crashes CompilerError.ToString in the .NET framework
[AspNet] Fix type resolution when multiple registrations use same prefix

BXC21885 - UpdatePanel incorrectly added to the designer
as System.Web.UI.Webcontrols.UpdatePanel
[AspNet] Add some built-in control registrations
Fixed 'Bug 21898 - System.AggregateException: One or more errors
occured'.
I added some more exception checks to find errors in the assembly
browser more easily in the future. This particular one was caused by
calling a gtk method from a background thread.
[Ide] Fixed a bug in the type system assembly caching.
[NUnit] Use Nuget reference in project template
[NUnit] Update NUnit runner to 2.6.3

And reference it via NuGet
[Core] Default to .NET 4.5 for new projects
Fix issue with the same file being open twice.

If you have a file A open and then open a solution where file A is in
the user preferences, then file A will be opened twice.
Merge pull request #626 from lukaszunity/upstreaming/same-file-opened-twice

Fix issue with the same file being open twice.
[Nunit] Add missing nuget restore
[Ide] Bug21849-Xaml CodeCompletionWindow closes after char added(SharedProject)
CodeCompletionWindows closed after first char was typed because there were two undisposed instances of FormsEditorExtension. First instance displayed window and marked that it shouldn't autoHide but second instance didn't mark this(because it didn't show window) it hid window. Hence bug.
This happened because when .xaml file opens it calls InitializeExtensionChain. Problem occurred when ((FormsEditorExtension)ext).Initialize (this); was which calls SetProject(to set owner project of document instead of SharedProject) and SetProject calls InitializeExtensionChain again.
So in middle of InitializeExtensionChain loop of adding editorExtensions new InitializeExtensionChain came in and disposed 1st editorExtensions chain. But when 2nd loop finished rest of 1st loop continued(extensions after FormsEditorExtension).
So what this commit does it checks if documents editorExtension is different from this InitializeExtensionChain call. And if different it disposes all editorExtensions in this call.