Turn Proportional Editing by Holding "Alt" just like "Ctrl" for snapping

Just like holding the "Ctrl" key turns on snapping temporarily, Holding down "Alt" key should enable proportional editing and with scroll wheel it should adjust the fall off. Additionally holding down Alt+Ctrl and scroll to change different fall off options. the fall off should be reset everytime so the user can change the effect of it gradually.

This is required as we sometimes want to initialize proportional editing while moving