don't crash when fromNode is 0 for some reason

(it was a cyberdisk)
some code clean to remove warnings
If deleting last save from load menu, don't show it any more.
Merge branch 'master' of https://github.com/xanscale/OpenXcom.git
Merge pull request #374 from hmaon/nodesel_crash

don't crash when fromNode is 0 for some reason
Merge pull request #383 from rohitnirmal/load-delete

If deleting last save from load menu, don't show it any more.
yet another fix for research popups.

if the base's available research has dependencies on this research,
or if the base's available research is unlocked by this research,
and it isn't unlocked by another discovered research or it's dependencies,

then unlock this research, and possibly it's dependencies, depending on if
the discovered research unlocks the dependent research in question.

simple, right?
motion scanners work in three dimensions

even though they only have 2d displays.
random gui changes

mostly to do with mousewheel/scrolling behaviour
make aggressive retaliation a little more aggressive.
fix end of turn terrain explosion
no more "died of fatal wounds" messages from terrain explosions
no more double explosions
don't explode the tile that explodes, it just exploded.
revert previous commit.

or at least part of it.