Post processing / diagnosis of ocp solutions

[PierreMartinon]

Gives more detailed information about a solution

• sort constraints (pointwise and path) and display violation and multipliers (use norm for path constraints). Plots ?
• We can't for the moment recorver the boundary conditions
• norms 1 and 2 of the control (component wise ?). NB. Can be displayed also in callback
• display running cost w.r.t time

Also provide a comparison tool for multiple solutions

• plot functions on same graphs
• display norm of errors between variables (objective also)

[jbcaillau]

@ocots Is it possible to add savefig for plots? I am assuming that Plots.jl is imported, so I guess it is just a matter of re-exporting savefig from the standard backend.

NB. Until so, I have added the dependency to Plots.jl (also to Markdown.jl