RcpApplication could not be found will occur even the org.eclipse.update.configurator is in the right place. If the RCP is unzipped from the RCP SDK, there is a folder "configuration" with a config.ini in it. Delete the config.ini, and no Exception will come up. 

java.lang.RuntimeException: Application "org.eclipse.ui.tutorials.rcp.part1.RcpApplication" could not be found in the registry. The applications available are: <NONE>.