Fix ScalableGraphFunctionTest

Geometry division logic changed. Test is now correct per design.
Fix select model element test.
Fix Formulas_FormulaCurve

Revit 2015 doesn't allow non-planar Nurbs curves. Not even in the hacky
way we could do them in 2014.
Fix test MAGN_3784

ElementTypes drop-down was not saved with the correct selection.
Changing it to ReferencePoint fixed a cast error in the test.
Fix InstParam sample tests.

Revit 2014 and 2015 returns different numbers of parameters in their
Family Parameters drop-downs. Saved index was off by two causing test to
pass in 2014 and fail in 2015. Replace drop down with string parameter
name.
Merge pull request #2533 from DynamoDS/2015-Test-Fixes

2015 Test Fixes