Support styling on back button on iOS (#3755)

* Removed possibleOpenGesture MMOpenDrawerGestureModePanningCenterView possibleOpenGestureModesForGestureRecognizer. This allows swipeable componenets like swipeable lists to be used on iOS.

* Revert "Removed possibleOpenGesture MMOpenDrawerGestureModePanningCenterView possibleOpenGestureModesForGestureRecognizer. This allows swipeable componenets like swipeable lists to be used on iOS."

This reverts commit f2500be9f7.

* Revert "Removed possibleOpenGesture MMOpenDrawerGestureModePanningCenterView possibleOpenGestureModesForGestureRecognizer. This allows swipeable componenets like swipeable lists to be used on iOS."

This reverts commit f2500be9f7.

* Allow styling of default back button on iOS.

lib/ios/RNNBackButtonOptions.h

@@ -8,5 +8,7 @@
 @property (nonatomic, strong) NSString* transition;
 @property (nonatomic, strong) NSNumber* showTitle;
 @property (nonatomic, strong) NSNumber* color;
+@property (nonatomic, strong) NSString* fontFamily;
+@property (nonatomic, strong) NSNumber* fontSize;
 
 @end

lib/ios/RNNBackButtonOptions.m

@@ -15,11 +15,36 @@
 		
 		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithImage:image style:UIBarButtonItemStylePlain target:nil action:nil];
 		[self setBackItem:backItem onViewController:viewController];
-	} else if (self.title) {
-		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithTitle:self.title
+	} else {
+		NSString *title;
+		
+		title = self.title ? self.title : viewController.navigationItem.title;
+		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithTitle:title
 																	 style:UIBarButtonItemStylePlain
 																	target:nil
 																	action:nil];
+
+		if (self.color) {
+			[backItem setTintColor:[RCTConvert UIColor:self.color]];
+		}
+
+		if(self.fontFamily || self.fontSize) {
+			NSNumber* fontSize = self.fontSize;
+			NSString* fontFamily = self.fontFamily;
+			NSMutableDictionary* textAttributes = [[NSMutableDictionary alloc] init];
+			UIFont *font;
+
+			if (!fontSize) {
+				fontSize = [[NSNumber alloc] initWithInt: 18];
+			}
+			font = fontFamily ? 
+				[UIFont fontWithName:fontFamily size:[fontSize floatValue]] : 
+				[UIFont systemFontOfSize:[fontSize floatValue]];
+			[textAttributes setObject:font forKey:NSFontAttributeName];
+
+			[backItem setTitleTextAttributes:textAttributes forState:UIControlStateNormal];
+			[backItem setTitleTextAttributes:textAttributes forState:UIControlStateHighlighted];
+		}
 		
 		[self setBackItem:backItem onViewController:viewController];
 	}