Make image complications template-able

[wtadler]

Is your feature request related to a problem? Please describe.
It would be nice if the icon and the icon color could be templatable and therefore dependent on HA sensors. For instance, in the below complication that shows my alarm status, it would be nice if the icon could show a shield with a line through it when the system is disarmed, and a plain shield only when armed.

Describe the solution you'd like
Make icon and icon color adjustable via template. I'm sure this could be extended to any number of other variables in the complications (i.e. #1163), but I imagine there is a tradeoff here with interface simplicity.

Additional context