Add `emcpy` as submodule to replace current plotting scripts

[kevindougherty-noaa]

Description

All of the plotting code has been moved over to EMCPy to be managed in it's own repository. Rather than have efforts duplicated in eva, it is best to import EMCPy as a submodule and utilize the plotting codes from there.

Adding EMCPy as a submodule is not necessarily a difficult task, but pointing to the right paths to allow the imports to work properly is proving to be a bit difficult.