Add OetcSettings.from_env() and forward solver options through Model.solve()#612

FabianHofmann wants to merge 5 commits intomasterPyPSA/linopy:masterfrom

feature/oetc-env-config-and-solver-forwardingPyPSA/linopy:feature/oetc-env-config-and-solver-forwardingCopy head branch name to clipboard