change RemoteValue to ABC and typecheck it

[farmio]

Description

typecheck xknx/remote_value/remote_value.py

Annotating its children (eg. RemoteValueClimate etc.) requires to also annotate most of the dpt module. I'll save this for later.

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have performed a self-review of my own code
• The documentation has been adjusted accordingly
• The changes generate no new warnings
• Tests have been added that prove the fix is effective or that the feature works
• The changes are documented in the changelog
• The Homeassistant plugin has been adjusted in case of new config options

[coveralls]

Coverage increased (+0.004%) to 94.777% when pulling 47487e2 on farmio:typecheck-remote_value into 30720c7 on XKNX:master.