Rebind CLI

Adds brooklyn command line args for persistence, e.g.

    ` brooklyn launch --app brooklyn.demo.WebClusterDatabaseExampleApp --noShutdownOnExit --persist auto`

and to rebind to that:

    `brooklyn launch --noShutdownOnExit --persist auto`

One can also specify `--persistenceDir /path/to/mydir`.

The possible options to `--persist` are:
* disabled - default, where there is no persistence
* auto - rebinds if data exists, otherwise starts up cleanly
* rebind - rebinds if data exists, otherwise fails
* clean - starts up cleanly, not using previous data

Note that old persisted data is moved to a timestamped directory, rather than being deleted.