DeploymentGenerator should allow AuxiliaryArchiveAppenders to return null Archives

Core assumes AuxiliaryArchiveAppenders are some what static and will return the same across the whole suite. This assumption is wrong, as a TestClass can be used to 'configure' a AuxiliaryArchiveAppender. e.g. Warp will return a null archive if TestClass has no @WarpTest annotation present.

https://github.com/arquillian/arquillian-core/blob/master/container/test-impl-base/src/main/java/org/jboss/arquillian/container/test/impl/client/deployment/DeploymentGenerator.java#L210

note: a more permanent 'disabling/enabling' of a Extension during executing should considered