Merge branch 'feature/migrate' into develop

* feature/migrate:
  Remove task count from task deques
  Customizable task migration and private deques
  Remove bulk tasks
tmp
simple
reschedule

Conflicts:
	src/libfleet/fleet.c
no index
shard
tmp
Afters

The new flt_after API lets you keep track of when a collection of tasks
all finish executing.
Check for theft after every task

Before each context would execute up to 32 tasks in a row before
checking whether someone else was trying to steal from it.  I think
we'll want theft to be more responsive, so now we check after every
single task execution.  It looks like we can do this without a
performance penalty by not inlining the code that actually migrates the
results over to the burglar.