Split global/task level arguments.

Move wrap.h,cc -> py-support.

Exponential backoff when scheduling.
Report elapsed kernel time back to master.

Track current execution in RunState; master needs more work.
Slight performance tweak; don't create run requests until we find
a free worker.
Tweak threadpool parameters.
A bunch of small fixes:

* Turn on profiling for combiner/reducer operations.
* Fix optimization passes (they were disabled due to a bug).
* Remove old wrapper files.
* Stencil (for now) reuses map_extents
* Add option for running workers under oprofile.
* Don't create a mask if a tile is fully specified.