HA integration: Fix knx.send to not coerce floats to int

[farmio]

Description

Changed the schema for the knx.send service to accept any value when type: is given. This way string, float, dicts, time etc. can be passed.
When type is not set the behavior is not changed -> coerced to int and treated like raw bytes.

Fixes home-assistant/core#44792

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 remained the same at 94.859% when pulling c22199b on farmio:fix-send-service into 01cd0fa on XKNX:master.