Only run error configuration once

[charleswaddell]

I wanted to move the error setup code out of configure since that method is called twice which could result in either multiple handlers of the same type being added or handlers being overridden that are added outside of the configure stage.

I could moved all the error handling setup into a handful of modules (example - SiteFileErrorModule, SiteSentryModule, etc.) but decided against doing that as we probably want to setup error handling as quickly as possible. That will allow us to handle errors that occur in the configure step which we wouldn't have handled before.

[gauthierm]

Minor feedback, setup is a noun. For the verb form for method names use setUpFoo.