This class must be implemented by the app to be compatible with HP Anywhere Apps framework.
This abstract class declares and inherits:
Returns the ServiceId from the descriptor XML file under WEB-INF/classes. If the ID is cached, returns the cached ID.
This implementation assumes that there is only one descriptor in the webapp (descResources[0]) and only one service in the file (getElementsByTagName("miniAppDescriptor").item(0))
Setsa string to be the new descriptor.