Plugin architecture

[Maxwell Rebo]

We'll need a clean, modular, extensible Plugin architecture. In particular these will be used to interface with third party tools, databases, other simulators (e.g. Gazebo), or provide custom data logging.

TODOs:

• Define plugin architecture and interfaces with other components/classes
• Define Plugin class
• Define sensible subclasses, e.g. LoggingPlugin, DBPlugin

Note that in these issues I use the terms "class" and "subclass" loosely with respect to Rust's particular flavor of OOP. They may simply be traits, or some other way of accomplishing the same thing.

[Francis Tseng]

Also (maybe this should be a separate issue) but some kind of Python interop for plugins would be really nice.

(edit: nvm, see that this is already covered by #2)

[Maxwell Rebo]

It should be relatively straightforward to create bindings that way. A simple sklearn example would be a good place to start, clustering agent behaviors or something.