Fix for selection box dragged out of canvas.

Fix for User gets stuck in selection mode when selection box is dragged
out of canvas.
Suppressed internal Revit classes by marking them internal
changes to mark internally used Revit classes as internal
Added a new skeleton class "QueryMirrorDataAsyncTask"
Removed "NodeViewModel.OldValue" property
Removed "EngineController.GetStringValue", it's not referenced
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into Query
changed method attribute
revert code change
Fix MAGN-5082 Dynamo does not notice if a change (delete or move) has occurred to an import instance
Fix for Selection box dragged out of canvas

Commented the mouse leave event on WorkspaceView.
Fix for selection box dragged outside the canvas

Removed the mouse leave event on Workspace view.
Captured the mouse event on LeftButtonDown and  released the mouse
capture on LeftButtonUp. This will ensure that selection is not lost
even when the mouse is dragged outside the canvas.
Handled the mouse lost focus event on DragCanvas. This will ensure that
selection is removed if the mouse is released outside the canvas.
changes as per review comments
prefer hiding in library to supress importing into VM
removed unused function
Added fix to recognize attributes applied to FFI properties
reformatting
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into dynamoCurrent
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into Query
Prevent engine reset during shut down sequence