Support additional menu items based on Moodle Mobile settings

This must be tested in a site with MDL-57410 applied. Login in the web as admin, go to Site administration > Mobile app > Mobile features and add some options to Custom menu items . Please make sure to add: 1 item of each type (embedded, inappbrowser, browser). Different languages for at least 1 of the items. A custom icon for at least 1 of the items. You should use a Ionicon class (e.g. ion-information, you can see the list in here ). At least 1 invalid item (less than 3 fields or any of the first 3 fields is empty). Login in the app and check that you see all the valid items in the side menu. Check that the language shown is the right one. If the item isn't configured in the current language, the fallback will be to no language and then to English. Check that the custom icons you configured are next to each item. If a custom icon wasn't supplied for a certain item, it should show the default icon. Go to App Settings and change the app's language. Check that the language of the custom menu items change if needed. Check that clicking 'inappbrowser' and 'browser' items open the URL in inappbrowser/browser. Check that clicking 'embedded' items open a new state with the page embedded. The embedded page should allow being inserted in an iframe, otherwise it won't work. E.g. moodle.org and prototype sites don't allow it. Now update any of the items in the site and then, in the app, login/logout or synchronize the site. Check that the custom items are updated.