Resources should be locked when open for editing

[brettatoms]

When an editor is opened on a resource then the server should be notified that it is open for editing and should prevent future changes to the same resource until it is unlocked. It could be as easy as visiting, .e.g. /family/1/lock and /family/1/unlock to lock and unlock a resource.

A table should be created to hold the locked states that includes the user who locked it, the time it was locked and probably other meta data about the lock.

We also need a mechanism to forcefully break locks.

[brettatoms]

Also see Bauble/bauble.api#15