Add support for left + right on DismissSwipeDirection

[darnfish]

What does this PR do?

• Add support for .left and .right to DismissSwipeDirection
• Add dismissOnRelease dismiss presented view on gesture ended (like a traditional UIViewController)
• Uses swipedAmount > 50% of VC rather than swipeLimit = 100
  • Also adds support for velocity-based dismissal, for when you quickly swipe the view away, but don't make it to the 50% limit
• Add support for overdragResistanceFactor (see https://github.com/IcaliaLabs/Presentr/issues/163)

[darnfish]

Lol I did not see https://github.com/IcaliaLabs/Presentr/pull/182 before making this, still keeping open as this PR provides some extra features :~) but it seems like the maintainer is not active