Allow SoftwareComponent to be added to MavenPublication
Added basic API and infrastructure for adding Maven Publications explicitly to set of publications
* Nothing is now published by default to maven repository without adding explicit publication
* Adding a component to a MavenPublication is optional
   * Publishing without component is currently broken
* Updated all tests for changed DSL
* This commit adds the API and infrastructure, but no work has yet been done to make the DSL user-friendly
WarPlugin now adds 'web' component, which can be published to maven repository.
Test tweak
Added support for empty publications to maven publishing
- Implementation is pretty ugly: need to see if there's a better way to add appropriate MavenDeployment when no artifacts added
- Might be worth removing ivy from the equation when publishing to maven - it just gets in the way.
Fixed integ test missed earlier
Integration test tweak