add remove_icon_theme_caches and adjust structure

tower: https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/6f6e3b1b4a7a4eab97b2b2e84550b37c/#7c1e6750b59a4731b9902c0bc89d8b57

Change-Id: Ifa2cfac0dca586118afcb00c0cea3830c1670005