Make some notable changes to how ``pecan.conf.app`` is passed to a new app.

* Now pecan.conf.app items are treated as keywords passed directly to Pecan
  apps.  This means no more tinkering with *both* your configuration file *and*
  your app.py file.
* Removed support for the RequestViewerHook config file shortcut (because now
  you can easily specify hooks via configuration).