RFR: Cleanup Shenandoah arguments

[Roman Kennke]

This change cleans up Shenandoah arguments:
- It fixes documentation
- Adds ranges to ranged args (incl. tests)
- Removes halfway, statusquo and lazy heuristics (which are only
specific sets of thresholds for dynamic). I also removed newadaptive,
which really also only was another set of thresholds. I wasn't sure
about adaptive, it's not useful either, at least not now, but I left it
in place as basis for future developments.
- Make dynamic heuristic thresholds product_rw and pick them values up
at each GC cycle, instead of caching them. This makes those values
possible to change at runtime via JMX. Should be very useful for
Thermostat
- Removed ShenandoahGCDetails, replaced the final summary with
-XX:+ShenandoahPrintStats, and all other ShenandoahGCDetails loggings
are already done through other options
- Removed ShenandoahParallelizeRoots. It's not the right way to achieve
that, and didn't yield the performance boost I was hoping for.

http://cr.openjdk.java.net/~rkennke/shenandoah-options/webrev.00/

Ok?
Roman