Clear flag set by gear on gear deletion. Also added a few more nil checks on HHGear

Make hedgewars frontend not change scheme/weps to Default if script cfg doesn't match a known scheme. That is, will leave on whatever is selected. Also set a bunch of schemes where we don't care what the scheme/weps are to *

avoid airmines too when spawning

bit more friction. remove gstSubmersible clearing. was for the old "sea" thing that is totally gone now. As a general attribute, better to let other stuff clear it as needed.

make mines submersible

oops, forgot this annoying thing