Use new loopback app features - app.restApiRoot, "start" event [DO NOT MERGE YET]

Requires strongloop/loopback#123
Related to strongloop/loopback-workspace#34 and strongloop/loopback-workspace#35

We need to bump up the minimum loopback version in package.json before merging this change.

/to: @ritch 
/cc: @sam-github