re-organising UI

[michbur]

• rename plots to deuterium uptake and split in subcategories specific to the plot
• add charge analysis after the input data
• add the about tab and HaDeX-related information (also funding)

[werpuc]

nested navbars menu requires changing the css. I found the solution online, but it is not working correctly when there is more than one nested navbar menu, so I included this in #109.