Switch to simple mode without fancy animation

I needed just simple side menu without that fancy animations, so for convenient added simpleMode property for turning simple mode on.

Other reason why I do so was that without fancy animation I wasn't able to force pan to stop at content offset value and not pan more. This functionality wasn't present.

Besides side menu dim wasn't working right. When i was swiping from side, dim from 1 to 0 was changing in respect to view width and not in respect to content offset value (old code 533 line).