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:

• Allow user to choose between

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

• Update (download) plugin icon rendering rules on startup

  • Enables updates and bugfixes withour new releases

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

  • Enables updates and bugfixes withour new releases

• 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: