Linux build script version set to 1.7.3
Refactoring and tests

- Matrix transformation of plane now moved to method on Plane3 rather than
  Matrix4. Matrices are generic objects and should not need to contain logic for
  transforming every possible geometric primitive.
- Plane transformation maths multiplied out to remove confusing double negation,
  no improvement to numerical accuracy.
- Added more tests
- Removed unused methods