Improve display image rendering.

[cgiesche]

I will re-write huge parts of the button image rendering to be more flexible and make it easier to implement new features.

Ideas:

• [x] Allow user to choose between

  • Plugin's icon
  • Icon from Home Assistant
  • No icon at all

• [x] Update (download) plugin icon rendering rules on startup

  • Enables updates and bugfixes withour new releases

• [x] Update (download) a list of states that represent an "active/on" state for image buttons

  • Enables updates and bugfixes withour new releases

• [x] Use color information from attributes if provided (for lights)

• [ ] Display cover-art or similar images from entities

• [ ] Allow users to override icon color Simple color picker?

• [ ] Allow users to override icon Dropdown / picker?

Related to:

211 #243 #242

[cgiesche]

Work in Progress: