Rewamp "clean" task

[andypost]

This task used to remove files which could be "re-builded" with composer/scaffold to minimize disk space used by project when it's not needed, also here we clean-up database files/dirs

More and more we store some additions in web/sites/*/ so we can't clean-up the whole dir

Initially we thought to store this additions in https://github.com/skilld-labs/skilld-docker-container/tree/master/settings dir but time shows that devs ignore it and put everything in sites

[andypost]

Basically we can delete all dirs (as root to remove read only files) and use git reset --hard to repair all commited files