Source file loading from sub-directories is sub-optimal

[fridis]

Currently, the a directory in any of the paths provided to the fz command via -sourceDirs are checked for sources as soon as a feature with that directories name is found, while the universe feature ensures that the outermost source files stored directly in the source directores get processed.

In conjunction with libraries, this does not work well since it requires iterating over the features in all libraries we depend on to find these directories. It would be better to iterate source directories and try to load suitable features in the libraries.

[michaellilltokiwa]

Since this issue is from long ago: @fridis is this still how you want things to be?