selinux: New rw privileges for themes

- New theme_data_file context for files under /data/system/theme
- Permit systemserver to create files/dirs under /data/resource-cache
- Permit systemserver to create files/dirs under /data/system/theme

Change-Id: Id597fc20b477ea395a8631623f26a7edde280799
(cherry picked from commit f27401910097d2084fafe36429f814c43841eccd)