Download kie-platform-bom JAR file with all dependencies

The BOM declares all internal and appformer dependency versions in dependencyManagement. KIE modules should _not_ directly import this BOM and instead use kie-parent and import specific KIE user BOMs. That is to avoid unnecessary dependencies on UberFire, Dashbuilder or Guvnor for non-UI repositories like Drools or jBPM. Platform BOM can be used in cases when one needs to easily inherit all the different versions KIE is using.