Automagic path following!

Only works on one-tile-wide (e.g. mapgen) paths.
Add fuses to remotely detonate dynamite.

Needs a sprite.
Fuses detonate neighbouring tiles.
Allow immediate triggering; fires ignite fuses.
Prevent placing fuses on water.
Add fancy but ugly fuse graphics.
Merge pull request #30 from FLHerne/master

fuses