Updating changelog
Release version 2.0.0.RC2
set to build snapshot version
SHDP-317 Better allocation localization

- Can now use relax localization flag
- Some obsolete settings removed from
  DefaultContainerAllocator, namely default
  hosts/racks properties.
- Adding some tests for allocation logic and
  request count tracking.
- new locality flag for launch context for
  containers, flag used in appmaster.
- AbstractBatchAppmaster now returns allocation
  garbage back to allocator. Using strict locality
  now creates garbage which we can't avoid in
  some cases.