xtcRunAll task respects xtcRun configuration, and it should just run everything in its source set output.

[lagergren]

In Xtc, every source set is given an runXtc task and a runXtcAll task. The latter should run everything runnable on the module path of the compiled source set, but currently it is identical to the runXtc task, which is intended to only run the modules configured in the xtcRun extension config (compare this to the analog application plugin for Java and the run tasks).

We should probably allow creating your own XtcRunTask types (requires refactoring out the xtc project delegate, but we need that to get the massive build speed increase the configuration cache gives us), and all other functionalities in the xtc tasks can override their global extension configuration.

Finally, would should allow nested modules sections, so that several modules can be associated with each other in some kind of group, and be treated in a special way, e.g. run in parallel.