core: Add no-arg constructor to Parameters classes

This is required in order to avoid potential serialization
issues with GWT RPC.

Change-Id: I54a256a7a9c36485630740d82bc0393561f9516a
Bug-Url: https://bugzilla.redhat.com/1029605
Signed-off-by: Vojtech Szocs <vszocs@redhat.com>