Dig smart: dig out minerals as you discover them. Very rough draft.
Merge branch 'master' into digSmart

Conflicts:
	plugins/CMakeLists.txt
digsmart temp commit.
Merge branch 'master' into digSmart
digSmart: still doesn't working, but learning more. Something weird happens with dig designations.
digSmart: framework in place for finding the bug. When a tile is actively being dug, the dig designation is cleared. If you designate the tile again for digging, multiple dwarves might try to dig it at the same time, leading to job cancellation spam when one finishes.
digSmart: added user interface and documentation.