Added test case for defect MAGN-3648
Remove dead code in core
First pass on geometry unit conversion framework
Correct call to Revit internal units
Correct call to UnitConverter when converting to Revit GeometryObject
Make conversion constants readonly
A bit of refactoring
Updated ImportInstance for unit conversion
Modifications to unit tests for unit conversion
Cleanup to RevitNodesTests and fixes for folder structure reorg
RevitNodesTests looks up ProtoGeometry at runtime, removed a number of unnecessary dependencies in RevitNodesTests
Do unit conversions for all types, unit tests for curve unit conversions, improved assembly reoslved in RevitNodesTests
Get all GeometryConversion tests running
Fix FloorTests due to errant ElementBinder deletion, failured to declare test filename
Fix to ModelTextTests for missing TestModel attribute
Fix to Graph Layout project to use props file

TBR @ikeough
Merge pull request #1789 from ke-yu/code_cleanup

Remove dead code in core
Merge pull request #1788 from riteshchandawar/Defect3648

Added test case for defect MAGN-3648
static readonly should be const in DynamoUnits
Added unit test for unit conversion in ImportInstance