Update pybench
Use jacobi preconditioner for Poisson benchmarks
Poisson benchmarks: default action to running benchmarks

Only save result on rank 0 when running in parallel.
Update params for Poisson benchmark

Create a series of meshes that roughly double in number of DOFs.
Add cell and dof count as metadata for Poisson
Poisson benchmark: add series for number of processes
Script plots for Poisson benchmarks

Combine a series of a parallel run over several processors and plot
the sequential result over mesh size and parallel scaling for each
parameter combination.
Only plot the assembly and solve times
Factor advection-diffusion into pybench benchmark
Used CG + Jacobi in advection-diffusion benchmark
Update pybench
Saving is now only done on rank 0
Log L2 error norm for advection-diffusion
Add scripts to run advection-diffusion benchmarks
Script data collation and plots for advection-diffusion
Force evaluation to get accurate timings
Update pybench
Add profile invocation for advection-diffusion benchmark