Refactor RCTUIManager

Summary:
Moved the view creation & property binding logic out of RCTUIManager into a separate RCTComponentData class - this follows the pattern used with the bridge.

I've also updated the property  binding to use pre-allocated blocks for setting the values, which is more efficient than the previous system that re-contructed the selectors each time it was called. This should improve view update performance significantly.

Examples/UIExplorer/UIExplorerUnitTests/RCTSparseArrayTests.m

@@ -25,10 +25,10 @@
 
 - (void)testDictionary
 {
-  NSObject<RCTViewNodeProtocol> *myView = [[UIView alloc] init];
+  id<RCTComponent> myView = [[UIView alloc] init];
   myView.reactTag = @4;
 
-  NSObject<RCTViewNodeProtocol> *myOtherView = [[UIView alloc] init];
+  id<RCTComponent> myOtherView = [[UIView alloc] init];
   myOtherView.reactTag = @5;
 
   RCTSparseArray *registry = [[RCTSparseArray alloc] init];