Making CMake tests "idempotent".
Makes it possible to re-run cmake tests without deleting existing files.
Most of these can be easily handled by setting UseSaveDM to false, but others required a dedicated fix (i.e. the MD restarts and the TBT test).
Now, EXTRA_FILES copies the files as part of the test command. In a similar vein, REMOVE_FILES is a new optional argument that removes files as part of the add_test command.
Closes #464 (closed)
Edited by Federico Pedron