RFR (S): Print the timings for conc bitmap cleaning

[Aleksey Shipilev]

Hi,

In our large-machine runs, we have quite a few cycles taken by concurrent bitmap
cleanup. Closer look identified that we don't report this important thing as
part of collection cycle, while we actually should. Fixed:
  http://cr.openjdk.java.net/~shade/shenandoah/times-print/webrev.01/

(This also fixes a few nagging UX problems, like s/Init-Mark/Init Mark/, etc).

Thanks,
-Aleksey