Add decorator for checking level of map input

[nabobalis]

In GitLab by @wtbarnes on Jul 9, 2021, 05:13

There are several places where we check the processing level of an input map (e.g. PSF deconvolution can only occur on level 1 data). We should implement a decorator that checks the processing level of a map and throws an error if it is not consistent with the specified level.

This could also accept logical operators (e.g. >=1,==1.5).