added in the el element in the constructors to allow usage before DOM loads. Also indented code a bit
merging from master into sudhanshu-jun26
path panel
added in virtualhelix.js, put in placeholders to trigger signals
slidebar and extendable,removable VHI
cleanup
slidebar bug fix
path panel integrated into html, slidebar bug fix
file removal
added in a collection for virtualhelix items
multi-layer slice panel
connected dom models to backbone views
slice panel zoom
added in undo/redo functionality at document level
minor pathview uncomments
merged branches sudhanshu-jun26 and sam-jun26 into head