Make full use of the propdeps plugin

Use the optional and provided configurations provided by the propdeps
plugin and remove specific handling of optional and provided
dependencies in pom customisation logic in favour of the
propdeps-maven plugin.
Merge pull request #35 from wilkinsona/generated-poms-again

Make full use of the propdeps plugin
Added the ability to provide multiple tags for ServiceInfoCreators. Refactored CloudFoundryServiceInfoCreator.accept into a set of composite methods so subclasses can easily override with a different composition.
Merge pull request #34 from scottfrederick/tags

Multiple tag support and refactoring accept().