Levelbuilding, bugfixing

locks/connections groups read properly in game,
tile interactions improved, level design progressing.
Bugs:
* Multiple-lock door not opening? (or is it because of node 0?)
* Electric tiles should have 1s delay before activating, and push
player back reverse of movement direction.
* Others?
Merge pull request #15 from theUPquark/master

Right-click delete and resulting lone nodes removed. Add buttons now add!
Merge branch 'working'
Merge pull request #14 from Silarn/master

3/15 Update 2