Repository.apache.org snapshot cleanup

[BRIAN FOX <br...@infinity.nu>]

For those projects currently using repository.apache.org:

We schedule daily cleanups of the snapshots, leaving behind 3 copies  
for a minimum of 10 days, the snapshots are removed when a release is  
published.

Otherwise, we don't have it setup to actively recreate the metadata as  
under normal conditions it should be managed by maven, but in  
situations like this it's certainly handy to repair with a few clicks.

The repository.a.o system is proxying the people snapshot repository.  
Snapshots for your projects on people should be removed when they are  
no longer relevant. During the migration, all snapshots were left in  
place. Once they are cleaned out from people, they will get purged  
from r.a.o after a few days of non-use.