Moved and renamed the starting and stopping scripts from the REST API
tests to a common directory. This way the MaxCtrl tests can use the same
scripts to start and stop MaxScale.
Also moved the test configuration file into the `test/` directory and
changed some of the default directory locations.
The script can now be used to run an arbitrary set of Node.js tests as
long as they define the `test` npm target. Refactored REST API tests to
fit into this framework.