Validate that JS and Native code versions match for RN releases

Summary:
Basic implementation of the proposal in #15271

Note that this should not affect facebook internally since they are not using OSS releases.

Points to consider:
- How strict should the version match be, right now I just match exact versions.
- Wasn't able to use haste for ReactNativeVersion because I was getting duplicate module provider caused by the template file in scripts/versiontemplates. I tried adding the scripts folder to modulePathIgnorePatterns in package.json but that didn't help.
- Redscreen vs. warning, I think warning is useless because if the app crashes you won't have time to see the warning.
- Should the check and native modules be __DEV__ only?

**Test plan**
Tested that it works when version match and that it redscreens when versions don't before getting other errors on Android and iOS.
Closes https://github.com/facebook/react-native/pull/15518

Differential Revision: D5813551

Pulled By: hramos

fbshipit-source-id: 901757e25724b0f22bf39de172b56309d0dd5a95

React/Base/RCTPlatform.m

@@ -12,6 +12,7 @@
 #import <UIKit/UIKit.h>
 
 #import "RCTUtils.h"
+#import "RCTVersion.h"
 
 static NSString *interfaceIdiom(UIUserInterfaceIdiom idiom) {
   switch(idiom) {
@@ -46,6 +47,7 @@ RCT_EXPORT_MODULE(PlatformConstants)
     @"systemName": [device systemName],
     @"interfaceIdiom": interfaceIdiom([device userInterfaceIdiom]),
     @"isTesting": @(RCTRunningInTestEnvironment()),
+    @"reactNativeVersion": REACT_NATIVE_VERSION,
   };
 }