327 some modules no longer import (#329)

* Test that all pyciemss modules can be imported.

Does a recursive sweep through the src/pyciemss tree and collects what look like modules,
then converts those to module names and tries to import them.
Reports ALL failures (does not fail on first issue).

* Removing import of non-existing function (it was also un-used in the module)

* Import fails due to missing petri_utils BUT bilayer_utils appears unused as well.

Conversed with JeremyZucker, he says bilayer_utils can go away.

* Reducing warnings in synth_data_utils.py