Map Tools - Mark radius

[Seb105]

Inspired by ~~idiot~~ treasured allies dropping mortars on friendlies, it seems a crew might mark on their maps certain distances around their location.

Maybe add a protractor item to allow this? Seems unecesssary so I've not done that here.

When merged this pull request will:

• Add an interaction to the maptool menu to allow a person to mark a circle of x radius about the "0" notch of their maptool.
• Does so in the selected channel and colour, and is deletable.