Themes: Reference app resource when compiling theme [2/2]

This allows us to pass in the path to the target apk as an additional
included resource apk, allowing theme designers to reference styles
and attributes from the original package without needing to duplicate
them.  Duplicating attributes never worked quite well, and causes
all sorts of issues, including crashing apps.

Instead of a theme declaring attributes, that are app specific, it
can simply reference the originals.  This way things like colors that
are style specific get included correctly.

Here's an example of stat_sys_wifi_signal_4_fully.xml using this feature.
By using ?com.android.systemui:attr/ we are able to reference attributes
defined in SystemUI directly in our themed resource.

<vector xmlns:android="http://schemas.android.com/apk/res/android"
    android:width="17.25dp"
    android:height="18dp"
    android:viewportWidth="46.0"
    android:viewportHeight="48.0">

    <path
        android:fillColor="?com.android.systemui:attr/backgroundColor"
        android:pathData="M20.4,18.0"/>
    <path
        android:fillColor="?com.android.systemui:attr/fillColor"
        android:pathData="M42.0,32.0l0.0,-4.0L26.0,18.0L26.0,7.0c0.0,-1.7 -1.3,-3.0 -3.0,
        -3.0c-1.7,0.0 -3.0,1.3 -3.0,3.0l0.0,11.0L4.0,28.0l0.0,4.0l16.0,-5.0l0.0,11.0l-4.0,
        3.0l0.0,3.0l7.0,-2.0l7.0,2.0l0.0,-3.0l-4.0,-3.0L26.0,27.0L42.0,32.0z"/>
</vector>

Change-Id: Icc794da9af2cd48099d42f9d7fbadaad8612b5db
TICKET: CYNGNOS-1645