[firedrake] Copyright consent forms needed before merging code back to FEniCS

As described at http://fenicsproject.org/contributing/contributing_code.html "Before your contribution can be accepted into FEniCS, you must sign a copyright consent form. Ideally, both you and your employer should sign a form." If anyone of you who have written code that is to be merged back into FEniCS components at some point have not already done this, if you do it now while I'm here you can avoid the snail mail. Martin