make it easier to run the test suite

[fstamour]

• add ":in-order-to test-op" to the system cluck
• add the corresponding ":perform test-op" to the cluck-tests system
• add a cl script to make it easier to run the tests regardless of where the project was cloned
• add a makefile as a simple entrypoint
• add a paragraph in the readme explaining how to run the tests