Add raftJoin and recovery options to init

[naimo84]

At work we're using two vaults. One for autounseal and one for the "real data". The one for autounseal can be initialized as usual with secret_shares, the data one has to be initalized with recovery_shares options. This one is also a RaftCluster, so I added raft join.

https://www.vaultproject.io/api-docs/system/storage/raft https://www.vaultproject.io/api/system/init#recovery_shares

Greets, Benjamin

[aviadhahami]

lgtm trying to get this in asap