Leaner dependencies

[poplarShift]

Hei, I'm frequently frustrated by the extensive imports that opendrift requires. While I am happy to disregard the environment/requirements file that is shipped with opendrift, for running a simple tracking experiment one should not require imports of matplotlib, colored logs, cmocean, etc. etc.

I am happy to make a draft PR but would be happy to hear your opinions first. Are simple try/except clauses with the appropriate warnings good enough for you or would you like some more advanced system with e.g. flags?

[knutfrode]

Hi,

We agree that a bare minimum of imports should be made.
We are planning on moving most of the analysis functionality (including plotting/animations) out of OpenDrift and into the TrajAn tool, which could help to avoid importing e.g. matplotlib for doing a simulation.
Presently plot-methods are in the basemodel module, and therefore libraries for plotting are also imported at the top of that module, according to PEP8:
https://peps.python.org/pep-0008/#imports

Pull requests for limiting unnecessary imports are welcome.
But probably best if you first make a small example PR, as @gauteh and myself could have some opinions or suggestions before merging major changes.