Added abstraction for creating TaskFactory's to ease testing.
Added additonal check in Test - check for prescense of mixin code behind file
Changed how threading works to ease testability.  Impact on performance should be minimal.
Fixed test name
Fixed bug where OnItemSaveCodeGenerator was generating code behind files for all files
Renamed Test class
Added new Tests
rebase (+1 squashed commits)

Squashed commits:

[8bdd4bd] Moved CompilerResultsExtensions to Common project
Moved logic for generating list with compiler error messages to extension method
Updated Tests to Compile and Execute mixed in method.
Created new Test NewDependenciesAreDiscovered
Added Test notes