Consider using visible configurations for resolving imported boms

[wilkinsona]

The configurations that are used for resolving imported boms are current hidden. This means that they don't appear in Gradle's dependencies output and are also hidden from things like the Versions Plugin. It would be interesting to explore the possibility of using visible configurations instead. This would allow new bom versions to be identified by the versions plugin and would also make it easier for people to work with the imported boms and manipulate their resolution (#221).