Update versions for 7.1.0-SNAPSHOT
ISPN-4939 Always include the clean goal as part of the lifecycle of the uberjar builds to avoid stale data
Remove references to old unused profiles in the documentation and the release script
ISPN-4939 fix missing uberjars from distribution zip and add back the extras profile to fix missing source artifacts
Implement purgeOnJoin

The joiner will still do the preload, but the entries will be removed from
the data container.

Also includes a fix for ISPN-3217 (entries not written to the cache store
on a backup owner with CACHE_MODE_LOCAL).

A hack was needed to avoid triggering ISPN-3443 (state transfer undoing the
remove operations).