How to set up the test runner

[ngm]

Currently the test runner is codeception. But this should be changeable (theoretically) from project from project.

It should probably be a config option then. And if we pick a particular option, running 'runtests' should do a basic smoketest to see whether that test framework appears to be in place.

[ngm]

I've made it come from the config file as to the command to run for the test runner.

(It could probably be improved, e.g. multiple configurations could be available and then you pick one, but good enough for now.)

However, still need a simple way of actually getting the test infrastructure into place. That should probably be the task of the developer, not aplet, but it would be nice to have a shortcut as it's a bit cumbersome to repeat over and over again (at least while I'm testing...)

[ngm]

Just wrote a basic bash script for now to copy the codeception files from another repo I have, then run composer install. Works for now but need to think if this is something the aplet should do or not.