iOS_SDK: add one more constructor to just take appId and launchOptions

Xamarin does some strict enforcement for parameters at runtime.
It was agreed that there needs to be a constructor that just takes
the OneSignal application id and launch options, but not the notification
handler callback.

Author: Vivek Ayer

iOS_SDK/OneSignal/OneSignal.h

@@ -61,6 +61,8 @@ typedef NS_ENUM(NSUInteger, ONE_S_LOG_LEVEL) {
 
 - (id)initWithLaunchOptions:(NSDictionary*)launchOptions autoRegister:(BOOL)autoRegister;
 
+- (id)initWithLaunchOptions:(NSDictionary*)launchOptions appId:(NSString*)appId;
+
 - (id)initWithLaunchOptions:(NSDictionary*)launchOptions handleNotification:(OneSignalHandleNotificationBlock)callback;
 
 - (id)initWithLaunchOptions:(NSDictionary*)launchOptions appId:(NSString*)appId handleNotification:(OneSignalHandleNotificationBlock)callback;

iOS_SDK/OneSignal/OneSignal.m

@@ -102,6 +102,10 @@ - (id)initWithLaunchOptions:(NSDictionary*)launchOptions autoRegister:(BOOL)auto
     return [self initWithLaunchOptions:launchOptions appId:nil handleNotification:nil autoRegister:autoRegister];
 }
 
+- (id)initWithLaunchOptions:(NSDictionary*)launchOptions appId:(NSString*)appId {
+    return [self initWithLaunchOptions:launchOptions appId:appId handleNotification:nil autoRegister:true];
+}
+
 - (id)initWithLaunchOptions:(NSDictionary*)launchOptions handleNotification:(OneSignalHandleNotificationBlock)callback {
     return [self initWithLaunchOptions:launchOptions appId:nil handleNotification:callback autoRegister:true];
 }