Picketbox layer

Because we want at some point to get rid-off this dependency, I am
wandering if we should really define a layer for it. Could be that any
dependency on it would imply the use of legacy-security layer. Picketbox
is implicit when legacy-security layer is provisioned.

The independent use is the management vault. Using that shouldn't require everything in the current p-b module though. And arguably you could say that use case means you need the vault tool and thus whatever layer has it. (You don't need the vault tool though, not on the server.)