Fix bug with parold specification not working.

The original switch statement was faulty, and prevented explicit
-XX:+UseParallelOldGC from being set.  We hadn't noticed this in the
past due to focus on "latency sensitive cases", which mean somewhat
of tunnelvision to CMS.
Merge pull request #33 from arbeitspferde/feature/strategy-cartesian

Explicitly name garbage collection strategies.