Rewrite and simplify code

[basnijholt]

I have simplified and rewritten a lot of the code.

In addition, I have added the functionalities:

• add only_once option to switch, which makes the light change to the correct value only when turning it on (or disabled_state, sleeping_state switch). This is useful when you want to manually change the settings of the lights sometimes and make it stay.
• add ability to make sleep_state and disable_state lists of options. For example when using an input_select where something should be disabled on multiple states. This is a non-breaking change because it also accepts just a single string.
• The switch is now fully async, which means that when adjusting the lights, all lights get the service call simultaneously.

[claytonjn]

Thank you, this was much-needed. I built this upon the flux component because I had never programmed in python before so things had definitely gotten quite messy. Will test ASAP.

[basnijholt]

@claytonjn, I wrote you on Discord. Maybe it's easier to discuss things there 😄