Provide dependencies for the plugins

[cr-xu]

In the main Badger repository, the requirements are only those needed to run the badger itself.
The packages required to run the plugins are not directly installed when setting up badger so one needs to figure out the dependencies themselves.

A bonus feature that would be nice to have: The ability to provide install options to badger directly, something like pip install badger[all-plugin] which installs all the necessary packages automatically.