Save files inside a solution folder project

-Fix issue #33 by loading projects that are inside solution folders. the
Projects property only returns the top level projects
- Add protection against ActiveDocument possibly being null
- Fix a InvalidOperationException inside CommonHintView
Fix thread related InvalidOperationException's

-Could not get RxApp.MainThreadScheduler to work with GoToElementState
so added a manual call to Dispatcher.BeginInvoke
- Adding observe on MainThreadScheduler fixed an exception related to
setting reminder opacity property
Fix TFS save issues

Issue #20 details problems saving TFS items including:
- Items are saved in the middle of entering descriptions
- Saving actually submits a work item to the TFS server
This commit includes code to detect TFS documents and prevents them from
being saved.
Cleanup: (re)move usings from inside namespace
Update All The Things
Fixups to move to RxUI 5.4
Fixes the CompositionException when loading

Changes Rx version to 2.1.30214 to fix the assembly loading error that
was causing the CompositionException when SaveAllTheTime was loaded.
Make sure the MainThreadScheduler is set properly

Fixes an issue when running SaveAllTheTime with ReSharper where
ReactiveUI detects it is running in a test runner, this causes the
MainThreadScheduler to not run subscribe delegates on the dispatcher in
some cases where required
Merge pull request #34 from davemckeown/fix-issue-33

Fix Issue #33 and #20