Retrieves the URL to the named resource. This can be used, for example, to locate configuration
or authority files. The resource should be declared in the <externalResourceDependencies>
section of the descriptor.
Note that if the URL contains spaces may be encoded as %20. The
URL#getPath() method
does NOT decode these sequences, therefore it is not safe to call
getResourceURL().getPath()
and attempt to use the result as a file path.
Instead, you may use
#getResourceURI(String) or
#getResourceFilePath(String).
For backwards compatibility, if the key is not declared as a resource dependency, it is looked
up directly in the
#getDataPath() and the class path. However, this usage is
deprecated and support may be dropped in future versions. ALL external resource dependencies
should be declared in the descriptor.