FIX: prevent silent errors on add/undo error

prevent silent errors in the dashboard due to an b2g-desktop instance stalled:
- call simulator.sendListApps on add/undo error to immediatelly list the new app
- update and check cached manifest before validation (to be able to update the app name in the dashboard)
- define a new app.validation.running attribute
- dashboard app validation result text: RUNNING, WARNINGS, INVALID, OK
   
should fix #374 and #365