added and implemented RevitServices project
updated controller to use RevitServices
added RevitServicesTests project
cleaned up TryGetElement code

Conflicts:
	src/DynamoRevit/DynamoController_Revit.cs
	src/DynamoRevit/Nodes/Annotation.cs
	src/DynamoRevit/Nodes/dynCurves.cs
	src/DynamoRevit/Nodes/dynDatums.cs
	src/DynamoRevit/Nodes/dynFamilies.cs
	src/DynamoRevit/Nodes/dynViews.cs
build fix
element validity checks now use RevitServices
added RevitServices unit tests
updated build settings to use props file
Merge pull request #514 from ikeough/RevitServices

Refactored Transaction management and element validity checking into separate RevitServices library