Implement locking for other process

Implement locking for other process

Locking for another process means that a longer running process (most likely
wb) wants to do several steps at once, and manages the locks.

Added parameters are:
    --lock-for PID: Locks the database for the process with this pid
    --unlock-for PID: Unlocks the database for the process with this pid
    --act-on-behalve-of PID: Ignores the log (if it is held by this pid)