Mass re-factoring of the polyglot-scala module

Mass re-factoring in support of a new DSL. Noteworthy:
* upgraded Scala to 2.9.2 with incremental compilation
* uses Specs2
* uses Kiama for pretty printing
* takes on a functional dsl
* Xpp3Dom configuration elements are modelled as Scala Xml elements
* improved gav and dependency declarations using an sbt like syntax, and the sbt cross compile convention
* used type classes to factor out the concern of pretty printing model objects
* minimised compilation of pom.scala files in order to perform well - only changes are compiled

Thanks in particular to @jroper, @richdougherty and @jsuereth for their reviews.

This PR is ready for merging with the caveat of the remaining domain classes needing to be done:
* Issue Management
* Licenses
* Mailing Lists
* Organization
* Prerequisites
* Profiles
* PluginRepositories
* Properties
* Reporting
* Reports
* Repositories
* Scm