Carousel

- Fixes 37
- add tests for `XLRDReader`
- fix data meta class parameter test to compare file approach vs. code

- pvpower demo formulas
- clean exceptions
- pvpower demo data
- pvpower simulations
- units as calcs
- sim thresholds
- uncertainty
- change name to carousel

- quickstart script to make filestructure
- packaged as wheel with docs unbuilt