Iflag

Fixed
- Index9 was not parsed correctly due to misinterpretation of documentation.

Changed
- Since different Corus firmware version have different parameter ids and different
data database layouts the library is rewritten to be less opinionated and work with
all firmwares. This means the user needs to know what ID represents what data and
how it is interpreted and how databases the they will read are structured.

Removed
- Removed internal session handling as it was in the way of optimizing running several actions
directly after each other. Instead now you need to call `client.startup()` in the
beginning and `client.shutdown()` when you are done.

Changed
- Separated value identification in parsing config for the different databases so that
it is possible to know if for example an average value is the monthly or hourly average.

Fixed
- Fixed error in setup.py that listed the wrong dependency. (attr instead of attrs)

Added
- Initial implementation of reading and writing data to Corus device.