Improve styling and enable URL parameters

[tranberg]

Everything now looks much better. I've only changed styling. No changes to layout or functionality. All settings seem to be working locally for me.

[tranberg]

It's now possible to set any of the parameters via URL parameters e.g.:

http://127.0.0.1:5002/?year=1990&country=DK&scenario=2050&freq=30

The advanced cost parameters are not supported yet.

It's optional which parameters are specified in the URL. The ones that are not/incorrectly specified will default to the default values from before this pull request.

Also, when the site is loaded the default results are not shown. Figures appear upon successful solving. I introduced a button to show a screenshot of the default results instead. This removes any possible confusion, since visitors might think that the results displayed upon initial loading correspond with the URL parameters - which is not true yet.

[nworbmot]

Cool, thanks Bo! Will play with it this morning.