Property now has move semantics

Properties are now moveable to enhance performance.

Also copy constructor is fixed.
Moved Property.h to include/
Added gtest unit test framework

Added gtest unit test framework.

Added a SigmaTests project.

Added a basic test file for Property.
Forgot the gtest.lib
Fixed SigmaTests and gtest runtime choice conflict
Update the README and test.sc files

The readme now has some more instructions.

Test.sc has been simplified.
Removed hard-coded paths to shaders