If source files are defined using relative paths, CMake will compile the tests, but this script will (sometimes) fail to find and parse the tests from the source files. I have added an explicit warning when ParseAndAddCatchTests fails to find a source file.
Added cmake script to parse the source files containing Catch's test and generate ctest definitions.
It generates one ctest test per `TEST_CASE` and labels them, using the `TEST_CASE`'s tags.
Closes#719.