Themes: Add ability to apply color filters to composed icons

Themes can include one or more of the following filter tags in

assets/icons/res/xml/appfilter.xml

    <!-- HUE filter

         Integer value between -180 and 180 representing the degree.

         0 = no change

    -->

    <filter name="hue">0</filter>

    <!-- SATURATION filter.

         0 = grayscale, 100 = no change, 200 = over saturated

    -->

    <filter name="saturation">0</filter>

    <!-- BRIGHTNESS filter.

         0 = pitch black, 100 = no change, 200 = 200% brightness

    -->

    <filter name="brightness">100</filter>

    <!-- CONTRAST filter.

         -100 = minimal contrast, 0 = no change, 100 = maximum contrast

    -->

    <filter name="contrast">100</filter>

    <!-- ALPHA filter.

         0 = transparent, 100 = opaque

    -->

    <filter name="alpha">75</filter>

    <!-- INVERT filter.

         Valid values are true or false

         true = invert colors

    -->

    <filter name="invert">false</filter>

    <!-- TINT filter.

         A hexadecimal value representing ARGB

    -->

    <filter name="tint">#ff0000ff</filter>