RFR: dynamic/static heuristics fixes, pack of 3

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/heuristics-static/webrev.01/

This includes several small adjustments to "dynamic" / "static" heuristics:

 a) "Rename dynamic heuristics to static": This alleviates confusion against "adaptive", and better
reflects the static nature of the heuristics that only watches the static thresholds without
modifying them.

 b) "Static heuristics should use non-zero allocation threshold": the comment hopefully explains it.
There are cases when static heuristics starts running back-to-back cycles otherwise.

 c) "Static heuristics should be really static and report decisions": this makes static heuristics
disregard CSetThreshold (which is mostly dead anyway), and start the cycle based on free/allocation
thresholds only

Testing: hotspot_gc_shenandoah (String dedup tests still fail), misbehaving benchmarks

Thanks,
-Aleksey