Unit test for TimeClusterTrigger.cxx

Added folder, CMakeLists.txt and source files for a simple unit test of TimeClusterTrigger.cxx

The test fills an input vector with equally spaced (digi) time values, runs the trigger algorithm, then compares the result with the expected one.

Update:

Also added a unit test for EventBuilder.cxx

This test uses an artificial time slice with sts digis, which are equally spaced in time, and reconstructs events from this time slice.

@v.friese @f.uhlig