Additional tools for smart images

[Acenoid]

I don't care that vtt is out of scope, I request it anyway stuff for smart images.

- Define one (or more*) measurements for the image
- ruler that works with the given measurement
* some maps have "zoomed" areas, so there you want to use the other measurement number that has been defined.

- next to the ruler could be circles / cones with varying degrees and such stuff.
- it would be nice if these tools could be drawn temporarily on the picture (but this would require another layer)

- various small tokens / colors to move around on the map. They could be selected from a category and linked to a topic.

- A switch that toggles between "pin" view and combat view. Pins are hidden and tokens & cones and stuff is shown. This is indepently of the GM-layer.

- pins can be shown either in their default icon, with the topic icon or some other custom icon that can be defined. There should be a small galery of default icons: ?, !, x, i, a skull, chest and so on

- it would be nice if the fog of war color could be adjusted

- Allow configurable hotkeys to navigate / select things on the smart image for example each tool available should have a hotkey.