Extracted styles for title and message into theme declaration

This PR allows simpler way to customize title and message text by overriding theme properties.
It also gives simple way to add title and message icon by using drawable[Left|Right...]

example:

    <style name="SDL.TextView.Title.Alert">
        <item name="android:drawableLeft">@drawable/ic_alert</item>
        <item name="android:textSize">16sp</item>
    </style>