Improved testcases and minor modifications for multiproject builds

Hi Magnus,

our Hackergarten contribution. We have some ideas for more improvements but I would like to keep the changes small enough for you to verify them.

One question that aroused, is the dependency tree for the subprojects. Currently dependencies of subprojects are not listed and it is not clear what lighttable expects in this case. Maybe you have some ideas/suggestions how to improve this.

Some minor improvements that I may contribute the next time:
- Deletion of class files before executing test case
- Currently only direct children projects are examined. Iteration recursively over all levels of subprojects.