Add Requirement for Storage Policy Names

With recent patches we've added exposure of policy names to clients
so to avoid confusion we have decided to require nameing them in
swift.conf (before you could get away without a name).

Change-Id: I576f7e9e03be97addaae479f1865fd7791581cc6
Implements: blueprint storage-policies
Merge "Add Requirement for Storage Policy Names" into feature/ec