thorium: store assigned workers inside actors

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
hash_table: add static to support private methods

Signed-off-by: George K. Thiruvathukal <gkt@cs.luc.edu>
Merge remote-tracking branch 'gkt/granularity' into energy

Pull branch from George K. Thiruvathukal:
  - This is the ongoing optimization work which consists in using
  'static' functions.
thorium_worker: add code that will be used for worker-to-worker delivery

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>