Reorganize analyze

[rouille]

Reorganize postreise/analyze.. We are leaning towards the following strucutre:

postreise/analyze/transmission contains congestion.py, mwmiles.py, statelines.py, utilization.py (renamed from transmission.py).
postreise/analyze/generation contains carbon.py, curtailment.py, summarize.py

The helpers module would stay in postreise/analyze for the moment since functions defined therein are grid related and hence could be used in both transmission and congestion analyses.

[rouille]

the design_transmission module in powersimdata/input/ imports the haversine function located in the mwmiles module. The latter module has been moved from postreise/analyze/ to postreise/analyze/transmission'. Thus a PR will be created in PowerSimData to fix the import.

[rouille]

The haversine function has been moved into the distance module now located in postreise/analyze/transmission. There two functions in this module now calculating the distance separating two locations. As mentionned by @danielolsen, only one should be used. This will be done in a future PR.