Add some guards / error messages around missing plugins / wrong profile setup

[alterNERDtive]

Common problems seem to be not installing EDDI and running the profiles directly, without including anything including the base profile.

Currently commands just assume everything is set up correctly; e.g. there are no checks if EDDI variables exist, they are just used. There are no checks if the base profile is active, commands are just (attempted to) run.

EDDI version exists once that is loaded, the base plugin would need to set its own flag. Checking in every command sounds like a PITA; the individual profiles are still setup to run their own startup command from way back when though. I should probably change that to a new command that just complains about:

• running profile directly
• not including alterNERDtive.base
• potentially not having EDDI

And I guess the base profile’s startup should/could check for all required plugins.