Reoarganize pint.utils

[abhisrkckl]

pint.utils is a whopping 3285 lines long without any organization. It's a bunch of widely different functions thrown together. We should reorganize it by

1. Splitting it into multiple files
2. Moving some of the functions into more sensible locations. For example, wavex_setup and dmwavex_setup should be in the pint.models.[dm]wavex namespace, IMO.

[scottransom]

Just putting a not here about it, but your post reminded me that I've been intending on making a PR to rename get_conjunction() in pint.utils. That name is way too ambiguous. Needs to be something like get_solar_conjunction().