Starting playground for dedalus+pySDC (#472)

* TL: started dedalus playground

* TL: main coupling done, need to adapt to new dedalus version

* TL: first working version

* TL: still need to solve problem with non-linear term

* TL: working version for one-level sweeps

* TL: minor changes

* TL: starting cleaning

* TL: adapted implementation to qmat switch

* TL: updated SDC version to be more efficient and allow variable sweeps

* TL: merged all sdc files into one

* TL: added mpi space-time communicator

* TL: minor debug

* TL: preparing for release

* TL: added RBC script

* TL: correcting a minor mistake