CB-8467

Added support for hiding the web view container.  This maintains the browser
session without closing it.  The browser window can be repeatedly hidden and
shown.

** This has only been tested on android and ios **

amazon/android:
An additional `hide` action was added to `InAppBrowser#execute`.  It is
identical to `show`, except that it calls `dialog.hide()` instead.

blackberry10:
no changes

firefoxos:
Added a `hide` method that is identical to `show`, indicating it is not
supported.

ios:
Added a `hide` method that is identical to `show`, except that it uses
`dismissViewControllerAnimated`.  It checks the value of
`_previousStatusBarStyle`.  If it is `-1`, the method returns with no
action performed.  If it is not, it is set to `-1.`

ubuntu:
Added a `hide` method that sets `CordovaWrapper.global.inappbrowser.visible` to
`false`.

windows:
Added a `hide` method that sets `browserWrap.style.display` to `none`.

wp:
Added a `hide` method that is identical to `show`, except that it sets
`browser.Visibility` to `Visibility.Collapsed` and sets `AppBar.IsVisible` to
`false`.

src/ios/CDVInAppBrowser.m

@@ -243,6 +243,54 @@
     });
 }
 
+- (void)hide:(CDVInvokedUrlCommand*)command
+{
+    if (self.inAppBrowserViewController == nil) {
+        NSLog(@"Tried to hide IAB after it was closed.");
+        return;
+
+
+    }
+    if (_previousStatusBarStyle == -1) {
+        NSLog(@"Tried to hide IAB while already hidden");
+        return;
+    }
+
+    _previousStatusBarStyle = [UIApplication sharedApplication].statusBarStyle;
+
+    // Run later to avoid the "took a long time" log message.
+    dispatch_async(dispatch_get_main_queue(), ^{
+        if (self.inAppBrowserViewController != nil) {
+            _previousStatusBarStyle = -1;
+            [self.viewController dismissViewControllerAnimated:YES completion:nil];
+        }
+    });
+}
+
+- (void)hide:(CDVInvokedUrlCommand*)command
+{
+    if (self.inAppBrowserViewController == nil) {
+        NSLog(@"Tried to hide IAB after it was closed.");
+        return;
+
+
+    }
+    if (_previousStatusBarStyle == -1) {
+        NSLog(@"Tried to hide IAB while already hidden");
+        return;
+    }
+
+    _previousStatusBarStyle = [UIApplication sharedApplication].statusBarStyle;
+
+    // Run later to avoid the "took a long time" log message.
+    dispatch_async(dispatch_get_main_queue(), ^{
+        if (self.inAppBrowserViewController != nil) {
+            _previousStatusBarStyle = -1;
+            [self.viewController dismissViewControllerAnimated:YES completion:nil];
+        }
+    });
+}
+
 - (void)openInCordovaWebView:(NSURL*)url withOptions:(NSString*)options
 {
     NSURLRequest* request = [NSURLRequest requestWithURL:url];