Mines and Gauss

This update adds a mine laying block. The mines last for 18 turns. I had a few cute ideas for what to do with them, but they're pretty good at just sitting there and stopping the enemy so they remain simple.

I've also added gauss-clouds. These don't hurt, but they will detach your blocks. Their slow movement means they are a simple obstacle or a chance to rid yourself of some ballast.

The gauss block can feed these clouds, letting you create a defensive net or rearrange your ship. I'll have to wait and see how broken this is. The enemy steers clear of clouds, you just end up sitting in your own purple haze. But perhaps someone might figure out a cheese for it.

In response to feedback on how disappointing the gauss block can be I've added an extra effect to the weapon. The detached block will now move to a random empty tile on being hit. You can use this to strip away the outside of an enemy with less chance of them docking again. Unfortunately I can't add this effect to the gauss clouds because they trigger at the end of a turn - a firing block acts at the start.

Some bugs have also been fixed.