Support for custom plant agents/currencies / appLogger debugging

[GregRRoss]

This is a draft pull request for back end changes needed to support the ACE agent editor.

Right now it still needs to be hardcoded for plants to work and it may not support other kinds of agents besides plants properly.

It also contains debugging app logger comments that will be removed before the actual pull, EDIT: And apparently some comments I left on the code trying to figure it out that I need to scrub away!

[GregRRoss]

Right now, the immediate issue I am working on in this branch is to make it so that if there is a custom agent created by the ACE editor but it is not selected in the config, it should not be sent to the backend.

Right now, based on the current state of the front and back end versions of ACE editor, it runs with custom plants, but if and only if the agents specified in the agent editor are also added as plants in the config.

[GregRRoss]

I have modified front_end_routes.py such that if a custom plant is in local storage (i.e. added via the ACE editor) but not selected from the setup wizard to start the simulation, that custom plant is removed from the configuration. This prevents the simulation from crashing.