Triangle-Triangle contact calculation.

- Returns the minimum penetration, which when offset, will remove the intersection.
- Added test cases.
calculateContactTriangleTriangle() updated to check degenerate triangles.

- Updated comments to explain variables and algorithm better.
- Removed unnecessary comments and corrected typo errors.
Removed #define surrounding calculateContactTriangleTriangle, put there
for testing.

- The #defines change the template funtion parameters to actual values.
- Uncommented the template line.
Fix cpplint warnings on spaces at end and front of lines.

- In Geometry.h and GeometryTests.cpp
Merge branch 'origin-master' into feature/TriangleTriangleContactCalculation

Conflicts:
	SurgSim/Math/UnitTests/GeometryTests.cpp
Changed comment phrasing to make better sense.

- "Closer" and "farther" vertex are used instead of "less deeper" and "deeper" vertex.
Changed the doxygen comment of a function variable.

- Referred a variable as an Abcissa, for better understanding.
Merge branch 'feature/TriangleTriangleContactCalculation' into 'master'

Triangle-Triangle contact calculation.

+1: Julien Lenoir

Merged-on: https://www.assembla.com/code/OpenSurgSim/git/merge_requests/587773