Proof that it works. :-)

 - cleaned up slf4j logging layer
 - using logback as sfl4j emitter
 - adding logback.xml to help troubleshoot things
 - removing 'core' from 'valve' project as it just pollutes the system vs
   webapp classloaders with duplicate classes
 - commented out use of raw 'core' in Main.scala
 - using simplified WebAppContext form