Add histogram visualisations

[jonc125]

Based on Aidan's code in the existing Web Lab - https://bitbucket.org/joncooper/fcweb/branch/cardiac-fitting

[jonc125]

(There's also the electrochemistry branch at https://bitbucket.org/joncooper/fcweb/branch/echem, but I think the plotting was copied from that to the cardiac branch.)

[jonc125]

Changes for this can be seen at https://github.com/ModellingWebLab/fcweb/compare/cardiac-fitting

[MichaelClerx]

Not priority for the workshop I think, where we'll focus on optimisation rather than MCMC!

[jonc125]

What output visualisation is needed for the optimisations for the workshop?

[MichaelClerx]

If it's really just optimisation then no output visualisation is needed, just the ability to show (print or write to file) the final parameters and possibly the error.

@mirams what do you think? Should we allow at least a "bad" (short, one chain) MCMC run, to stick closer to the theme of UQ?

[mirams]

Yeah it would appeal to the audience to see an MCMC histogram too, maybe put it at the top of the 'nice to have but not essential' list?

[jonc125]

Done in #173.