RCTTextField was spliited into two classes

Summary:
Motivation:
 * We maintain two different implementation of <TextInput> (multilined and singlelined), this change makes the implementations much similar which will help us to support and improve both of them in the (near) future;
 * We have to have separated RCTView-based container view for (TextField) to support sofisticated bordering and so on;
 * It opens to us possibility to unify UITextView and UITextField subclasses and remove code duplication across RCTTextView and RCTTextField;
 * Making things decoupled in general will allow us to fix existing bugs with events.

Reviewed By: mmmulani

Differential Revision: D5083010

fbshipit-source-id: 2f2d42c2244d2b39256c51480c1f16f4e3947c01

RNTester/js/TextInputExample.ios.js

@@ -773,6 +773,9 @@ exports.examples = [
                 backgroundColor: '#eeeeee',
                 borderColor: '#666666',
                 borderWidth: 5,
+                borderTopWidth: 20,
+                borderRadius: 10,
+                borderBottomRightRadius: 20,
                 padding: 10,
                 paddingTop: 20,
               }}
@@ -780,7 +783,7 @@ exports.examples = [
             />
           </View>
           <Text>Multiline TextInput</Text>
-          <View style={{height: 80}}>
+          <View style={{height: 130}}>
             <TextInput
               style={{
                 position: 'absolute',
@@ -788,9 +791,12 @@ exports.examples = [
                 backgroundColor: '#eeeeee',
                 borderColor: '#666666',
                 borderWidth: 5,
+                borderTopWidth: 20,
+                borderRadius: 10,
+                borderBottomRightRadius: 20,
                 padding: 10,
                 paddingTop: 20,
-                borderTopWidth: 20,
+                maxHeight: 100
               }}
               multiline={true}
               placeholder="Placeholder defines intrinsic size"