RFR (S): 8073052: Rename and clean up the allocation manager hierarchy in g1Allocator.?pp

[Thomas Schatzl]

Hi all,

  can I have reviews for the following change that does some renamings
in the allocation related class hierarchy, also adding a few lines of
documentation.

This change is intentionally limited to renames to keep it simple, in a
subsequent patch there will be more cleanup changes, moving methods
around.
Also, if there is demand, I am open to rename the files to something
different (suggestions?) in a follow-up change (to not confuse the
webrev tool too much).

CR:
https://bugs.openjdk.java.net/browse/JDK-8073052
Webrev:
http://cr.openjdk.java.net/~tschatzl/8073052/webrev.00/
Testing:
jprt

Thanks,
  Thomas