adjust `fre.cmor` to use `fremor`

[ilaflott]

like CatalogBuilder

this can't currently be fully implemented because of environment conflicts between cmor>=3.14.2 and cdo/python-cdo and nccmp

but the usage of fremor by fre.cmor is prototypeable, still.

• conflicts with cdo/python-cdo resolved
• conflicts with nccmp resolved