Move housekeeping into coreapp and cleanup more stuff

[mkst]

This update:

• removes unchanged fork-of-forks by non-anonymous users (to scratches that are adding no value) i.e. User 1 has scratch A, User 2 forks it creating B, and forks that to create C (so chain is A -> B -> C), we will remove C if there are no changes compared to B.
• clean up asm blobs from deleted scratches (asm does not get cleaned up when scratches are removed because one asm may be referred to by multiple scratches), so now we will clean up any orphans.