Fix warning in grails console

[nickdos]

When grails starts up, I see the following error in the console:

WARNING: The [options1] action accepts a parameter of type [au.org.ala.downloads.DownloadParams] which does not implement grails.validation.Validateable.  Data binding will still be applied to this command object but the instance will not be validateable.

       def options1(DownloadParams downloadParams) {
       ^
WARNING: The [options2] action accepts a parameter of type [au.org.ala.downloads.DownloadParams] which does not implement grails.validation.Validateable.  Data binding will still be applied to this command object but the instance will not be validateable.

       def options2(DownloadParams downloadParams) {
       ^
WARNING: The [confirm] action accepts a parameter of type [au.org.ala.downloads.DownloadParams] which does not implement grails.validation.Validateable.  Data binding will still be applied to this command object but the instance will not be validateable.

       def confirm (DownloadParams downloadParams) {
       ^

[charvolant]

Code review is all fine ...