Initial Merge Request

Hi @k204231 @k204229 @b324031 @k204225 ,

this MR is not really about a plugin but rather a submodule for various plugins. 'll What does this code do:

It is able to create various instances of maps (global maps / with lonlat bounds as well as maps on rotated poles). It also offers functionality to plot lon/lat data (xarray.DataArrys) on these maps.

The idea is to have this as a submodule for various plugins. To create a submodule in a plugin repository you'll have to use the git submodule add https://gitlab.dkrz.de/freva/plugins4freva/mapfactory.git command. This will add the mapfactory repository as a submodule.

You can see how this in the animator animator plugin I've just added as a test for this machinery.