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`.

www/inappbrowser.js

@@ -50,7 +50,10 @@
             exec(null, null, "InAppBrowser", "close", []);
         },
         show: function (eventname) {
-          exec(null, null, "InAppBrowser", "show", []);
+            exec(null, null, "InAppBrowser", "show", []);
+        },
+        hide: function (eventname) {
+            exec(null, null, "InAppBrowser", "hide", []);
         },
         addEventListener: function (eventname,f) {
             if (eventname in this.channels) {