magellan

Fixes CircularRevealTransition attempting to target non-existent views

Fixes CircularRevealTransition leaking memory and crashing on back press.

• Fixes onBackPressed called twice for navigables at the top of a navigator's backstack
• Support non-Activity contexts (ie. ContextWrapper)

• Adds extension functions to LinearNavigator for common navigation patterns.

• Support interrupting transitions to prevent overlapping animations in LazySetNavigator
• Make currentNavigable a recursive function of the current backstack
• Move afterNavigation trigger to post-transition animation
• Support custom navigable behavior in NavigationTraverser