Android WebView: cannot enable localStorage

The default implementation of WebView on Android does not enable the localStorage. Thus, it is not possible to start web app using it. 

File: QtAndroidWebViewController.java

Suggestions:

 1. (complex) Add a proper generic interface to enable various browser settings in the QML WebView component

2. (simple) Add the following lines in the constructor:

webSettings.setDatabaseEnabled(true);

webSettings.setDomStorageEnabled(true);

These lines can be surrounded by a check if the app permission allows it (write to external storage??).