* move imports to top-level in mqtt server
* move imports to top-level in mqtt configflow
* move imports to top-level in mqtt init
* move imports to top-level in mqtt vacuum
* move imports to top-level in mqtt light
* Recreate component if discovery info is changed
* Update component instead of remove+add
* Set name and unique_id in __init__
* Update unit test
* Cleanup
* More cleanup
* Refactor according to review comments
* Change discovery_hash
* Review comments, add tests
* Fix handling of value_template