Add Blocker Wall as suggested in http://powdertoy.co.uk/Discussions/Thread/View.html?Thread=17123
WIFI uses 16x less memory than before
Fix bug where Ctrl+X do not always function correctly (leaving some stacked particles not deleted)
fix bug where Blocker Wall don't work when replacing a wall on Blocker Wall
General changes for mods
fix SWCH particle order dependacy, edit IntroText, ignore updates, reset version number
Add Langton's Ant
Add element POWR, not stable at this moment. Not visible yet
fix glitch where SING eats things like CLNE
Remove ETRD conducting limits, allows ETRD to conduct with NBLE