Simplify killing processes.

* Do not hook rt_sigaction or signal (32 bit).
* Old "interrupted" logic is unnecessary since parrot-native-fd branch.
* New pfs_process_cankill (formally pfs_process_raise) which encapsulates the
  logic pfs_dispatch*.cc needs for handling the kill system call.
* Remove obsolete logic in decode_write for handling SIGPIPE, which was necessary
  before parrot-native-fd when Parrot handled all tracee pipes.
Add task termination status to result
Adds signal, resources exhaustion and task timeout as results
Changes status to exit_status at worker
Report task_status in result
Exit with an error if an auth method is unknown.

This confused some of our Physics friends because they were using -a=unix which
tries to:

    auth_register_byname("=unix");

which silently failed.
Simplify killing processes.

* ccl/pull/543/head:
  Simplify killing processes.

Conflicts:
	parrot/src/pfs_main.cc
Simple priority submission feature for WQ.
Modified send_one_task to iterate over the ready list, so as to keep tasks in priority order.
Factored push_task_to_ready_list so that all inserts follow the same logic.
Remove unused stoptimes.
Added priority to the python bindings.
Fix binding documentation.
Adds priority test.
Deprecates specify_task_order.

We could not gurantee the given policy. With the addition or
specify_priority, the queue works as if FIFO was specified.
Adds long options to chirp_get
Merge branch 'fix_chirp_get_options'
Merge pull request #558 from btovar/work-queue-priority

Work queue priority
Changes list priority from int to double.

This allows an easy implementation of something like A* in work queue,
while preserving the old int behaviour.
Merge pull request #535 from btovar/separate_task_result_exit_code

Separate task result and exit code
Expire tasks by end time, at the master