Restored explicit deps exclusion as per Burt's advice at http://burtbeckwith.com/blog/?p=1719
Moved spock sources to test folders in order to reduce spock dep scope from compile to test
Set legacyResolve to true in order to support maven-install from the release plugin: this seems needed in order to grant grails 2.2 compatibility, see http://www.objectpartners.com/2013/02/13/grails-2-2-publishing-your-plugins-as-maven-artifacts-to-resolve-dependency-resolution-issues/