Use Shelly "appliance type" setting to determine the switch icon

[cweiske]

The appliance type is a free text field, but Shelly v2 devices have a list of pre-defined types:

• lights
• socket
• heating
• entertainment

I've also added the christmas tree and the schwibbogen out of personal requirements :)

Icon sources (pixel icons unfortunately):

• https://icons8.com/icon/7283/wall-socket
• https://icons8.com/icon/Xt5q8KnCd00x/christmas-tree
• schwibbogen was made by me with my basic gimp skills

Screenshots

[cweiske]

I've rebased it against current master.