Core build split, stage one

This PR is the first of many that will be involved in spltting up the WF code base. This PR does the following:

- Adds a maven plugin that is responsible for building the WF distribution. This plugin will eventually be split into two different tools, a build plugin for building feature packs, and a provisioning plugin for assembling a server from feature packs.
- Changes our build process to use this plugin removing build.xml
- module.xml files now explicitly specify their resources, rather than in a single monolithic file
- build directory is now used to create a lightweight server without jar files being present that uses jars from the local maven repo, the dist directory now contains the full server.
- build now takes place in 3 stages, first the core is built, then a lightweight 'web' server, then everything else