styleable 'typeface' attribute, to allow setting typeface in theme

these changes allow setting typeface in theme:

in app themes.xml:

    <style name="Theme.MyApp.Text">
        <item name="android:textSize">12sp</item>
        <item name="typeface">font_name.ttf</item>
    </style>

   ....

in app layout.xml

        <com.neopixl.pixlui.components.textview.TextView
            style="@style/Theme.MyApp.Text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="THIS IS A TEST"
            />