Poisson: minor refactoring
Wave: minor refactoring
Firedrake forms coffee: pass through max_nf parameter

Closes #1
Poisson: make degrees configurable
Poisson: configurable base size for weak scaling
Poisson: add parallel efficiency plot for weak scaling
Wave: add parallel efficiency plot for weak scaling
Wave: configurable base size for weak scaling
Poisson: don't group by variant if there is only 1
Wave: don't group by variant if there is only 1