Update minimum required version of modeltree
Add support for runtime changes to settings

This is most applicable for testing and includes the
connecting to the settings_changed receiver
Add (missing) coded_values method
The Formatter class depends on this for mapping the raw value to a
code.
2.0.16 Release
2.0.17 Bump
Improve logging integration to log only once for the same field

Prior, every use of the formatter would result in a logged message.
Improve logic for to_number and to_coded methods

Add support for Decimal type
2.0.17 Release