Add remote-entity type in Integration-API

[zehnm]

This PR adds support for a "remote-entity" type in the Integration-API. This allows integration drivers to define generic remote commands to control any type of device, which cannot be represented by one of the other entity types.

The Home Assistant integration will be updated right after this PR is merged to expose the defined remotes in HA.

The remote-entity closely follows the existing internal IR-remote entity:

• Same features, with exception of the infrared codeset:
  • Physical button mappings
  • User interface pages
  • Simple commands if the integration provides a list of available commands.
    Note: unfortunately this is not possible for the existing Home Assistant integration.
• Core-API support to define button mappings and UI pages.
  • This is not yet supported in the web-configurator!
• Automatic button mappings and UI page creation based on simple commands (requires that the integration drivers follows the defined command naming patterns).

Changes to the internal IR-remote entity:

• Instead of the send feature, it defines the send_cmd feature:
  • Instead of the send and send_sequence commands, it defines send_cmd and send_cmd_sequence commands.
  • This allows specific commands for the web-configurator with additional parameters:
    • hold defines the button hold time (if supported by the integration driver & controlled device).

[zehnm]

Ready for review. The Python API wrapper library has been enhanced with a remote-entity support including an example. PR will follow.