Feature/better error message for oracle connector

Show custom help for missing oracle connector and improve the global exception view to always show the help message.

> Oops! Something is wrong
> Connector "oracle" is not installed.
> Add the connector to your project, configure the environment variables, restart Studio and try again. See [docs: Installing the Oracle connector](http://docs.strongloop.com/display/LB/Installing+the+Oracle+connector) for more information.

See #455.

/to @seanbrookes please review
/cc @anthonyettinger 

Collapsed view
![screen shot 2014-11-04 at 10 26 33](https://cloud.githubusercontent.com/assets/1140553/4897284/bc9f1ca2-6404-11e4-9d86-47cb001d3a17.png)

Expanded view
![screen shot 2014-11-04 at 10 26 42](https://cloud.githubusercontent.com/assets/1140553/4897287/c15c76cc-6404-11e4-830d-1f63c17c4e0d.png)