Offer help when plugins throw errors.

When things go wrong rendering a plugin the error is caught and a mysterious messaged displayed.

![screen shot 2014-05-02 at 8 26 03 pm](https://cloud.githubusercontent.com/assets/12127/2869478/eb9d7e46-d272-11e3-8626-0435e6ed1b68.png)

This commit adds a help button to the message. Help opens a dialog with some hints and an offer
to retry the errant plugin without the error recovery so that the inspector/debugger can do its thing.

![screen shot 2014-05-02 at 8 26 40 pm](https://cloud.githubusercontent.com/assets/12127/2869505/56bf122a-d273-11e3-961b-ace3ec753299.png)