Workspace: implement start/stop/restart

REST API:

    > POST /api/workspaces/start
    < { pid: 1234 }

    > POST /api/workspaces/stop
    < { exitCode: 127 }

    > POST /api/workspaces/restart
    < { pid: 1235 }
Merge tag 'v3.3.4'

3.3.4
fixup! implement isRunning, fix remoting data
Merge pull request #147 from strongloop/feature/start-stop-project

Workspace: implement start/stop/restart
3.4.0
Merge branch 'release/3.4.0' into production