The getTestCustomModules() method should not be used

Moving off that method, using new one introduced by
Stuart (customizeModules(List))
upgrade KZ to 0.5.4
[NEXUS-6286] Upgrade to siesta 2.x w/RESTEasy
Merge pull request #516 from sonatype/move-off-deprecated-method

The org.sonatype.nexus.test.PlexusTestCaseSupport.getTestCustomModules() method should not be used
Add jackson-datatype-joda module

As it's needed in some tests.