Adding an overridable DrawableFactory to allow creating custom icon drawables

> Adding ItemInfo as a parameter for creating drawable

Change-Id: I793acb0381d2b8df4db0a08317dddf1464788ebc
diff --git a/res/values/config.xml b/res/values/config.xml
index 5b3ee46..d270def 100644
--- a/res/values/config.xml
+++ b/res/values/config.xml
@@ -79,6 +79,9 @@
     <!-- Name of an icon provider class. -->
     <string name="icon_provider_class" translatable="false"></string>
 
+    <!-- Name of a drawable factory class. -->
+    <string name="drawable_factory_class" translatable="false"></string>
+
     <!-- Package name of the default wallpaper picker. -->
     <string name="wallpaper_picker_package" translatable="false"></string>