added watch object handling for Revit
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into MVVM

Conflicts:
	src/DynamoCore/ViewModels/DynamoViewModel.cs
	src/DynamoRevit/ViewModel/RevitWatchHandler.cs
Fix MAGN-4095 Getting crash while running Document after closing and reopening again.
Updated scheduler/async task namespace to "Dynamo.Core.Threading"
Added initial implementation of "DynamoSchedulerThread"
Implemented RevitSchedulerThread, referenced DynamoCore in RevitServices
Implemented a new "TimeStamp" struct for time keeping.
Merge branch 'SchedulerThread' into Concurrent
Merge branch 'Concurrent' into TimeStamp
Replaced "long" with "TimeStamp" struct that carries "TickCount"
Implemented "TimeStamp.Equals/GetHashCode" methods, updated test cases.
Remove redundant ast assignment
Change file share mode for License.rtf when reading it
Using FileShare.ReadWrite when reading a file
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into Concurrent
Moved "ISchedulerThread" into a separate folder/file
Merge branch 'Concurrent' into TimeStamp
Moved relevant files under "DynamoCore/Core/Threading" folder
Merge branch 'Concurrent' into TimeStamp
Moved "TimeStamp" class into a new file "TimeStampGenerator.cs"