General validation and A3 Family History Layout

[ashleybot]

In general

This PR provides

• [ ] Improvements to validation attributes to allow stacking
• [ ] Reintroduction of RequiredIf validator, but with a key change: it is for specific use and not overall form finalization
• [ ] Beginnings of form flow finalization (aka. partial saves vs completion)

For the A3

Fixes #26

This PR only resolves the layout of the form as described in the linked issue. Full functionality will be provided with the final card: https://github.com/UK-SBCoA/uniform-data-set-dotnet-web/milestone/3

Previous layout

New layout

Features:

• More condensed vertically so considerably less scrolling required (a request from end-users), but still maintains appropriate whitespace for usability
• Moves copy to clickable tooltip where appropriate (for example, codes for neurological problem/psychiatric condition)
• Removes use of color to align salience-importance relationship (ie. parent, sibling, children sections are not more important than any other field)
• Follows layout of paper form for content
• Removes visual clutter created by table cell borders

Other improvements

• Inputs are responsive an no longer are "cut-off" on smaller display sizes (previous UI on left, new on right)

[ashleybot]

@smiththay Can you take a look at my PR? I've added more things in here than just the A3 layout, but you can ignore the other stuff and just look at the layout.