Themes: remove unused code

Change-Id: I5ee8de962c40ddc5fcfbbc0332a9e389223e716c
Themes: Delete icon resources during uninstall

Change-Id: Icf247642f9d246c8826f3394f873e4b434ad2b3f
Themes: Update last postFinish call

* Previous patchset changed postFinish function signature.

Change-Id: Ibe07435e274054c7203504bc4b0877b4df006893
Don't cleanup overlay mapping for non-theme apps

mOverlay structure should keep all app/theme mappings even
if the app does not exist. Otherwise we will have to insert back the mapping
for every app that is installed which would be time consuming.

Without this patch an upgrade app loses its applied theme
until the device is rebooted.

Change-Id: Id02b8e0a3bdd78d1a9d39cd38294c584ef95f8db