rework Strategies, rename data classes

• new Strategies: CopertStrategy, HbefaStrategy, and HbefaColdStrategy
• renamed data classes: input_data to berlin_format and unified_data to yeti_format
• other: better tests, better docs

Multiple pollutants in one config

Users can now specify multiple pollutants in one config file:

pollutants: [PollutantType.NOx, PollutantType.CO]

This version is not backwards compatible. (Old config files using pollutant: ... will no longer work with this version.)

Better validation

Add validation functions for all Strategies for both modes.

Also: bugfixes.

Bugfixes

Merge pull request #10 from twollnik/dev

Dev