First approach for simplifying ps.send_recv logic, and common tag-comparing/checking

[jlnav]

Proposal to replace the common:

tag = None
while tag not in [STOP_TAG, PERSIS_STOP]:
   do_persistent_stuff()

with:

while not ps.instructed_to_exit():
   ...

---

Work , as returned by ps.send_recv() is only used by APOSMM for the Work["libE_info"]["H_rows"] purpose. This is probably sufficient for most persistent_gens:

calc_in = ps.send_recv(H_o)

---

After every recv, for APOSMM's purpose, the following attribute is now accessible:

ps.rows

so APOSMM can change (for example):

local_H["sim_ended"][Work["libE_info"]["H_rows"]] = True

to:

local_H["sim_ended"][ps.rows] = True

[jlnav]

This may be superseded by complete overhauls of "persistent" objects