Small error in LFPPDofHandling

[enricomiletto]

Hello,
I think for a S_2^0 space there should also be 1 dof for every quad, not only every edge.

https://github.com/erickschulz/NPDECODES/blob/47b4fe6d60640a10bfe0ed085d67a3ccdadac831/homeworks/LFPPDofHandling/mysolution/lfppdofhandling_main.cc#L33-L39

Cheers,
Enrico