Updated older Model class name with SiteSet for tutorial/04_mps
Renamed 05_DMRG tutorial folder to 06_DMRG to make room for new time evolution tutorial.
Removed an out of date comment
Made itensor namespace usage more correct for tutorial/04_mps
Fixed ShowPercent feature of TEvolObserver.h
Added new tutorial 05_gates
Removed const from tensor in 05_gates tutorial. Added a hint to the instructions.