add "startall" action

I would like to introduce "startall" action to forever.
This change lets forever be able to save a list of daemon settings in config.json and use "forever startall" to start all of them in 1 command.

This definitely helps managing multiple forever-ready daemons in 1 local server and reduces the risk of mis-operations.

Daemon list is saved in config.json like below:

    {
        root: '/aaa/bbb',
        ...
        columns: [ ... ],
        apps: [
            { script: '/xxx/yyy', options: [ ... ] },
            { script: '...' }
        ]
    }

Also there are 2 new actions to help adding/removing the list:

    forever apps add /xxx/yyy...
    forever apps rm /xxx/yyy...

Please let me know your thoughts.
Regards,