Layout panel updated for new design

[maxkfranz]

Improved layout panel with new design

• Lightning icon for layout panel
• The layout component contents fit the side bar now.
• Custom styling on top of Material UI: Less salient widgets use a different pallet from the existing theme. Several customisations are possible only by writing custom rules in our CSS to override what Material UI does. This second approach, for instance, is used to make the tabs look more like buttons.
• Widget spacing improved within the panel (e.g. sliders and section labels).
• Adds a 'reapply layout' button.
• For future: The UX of the layouts could use improvement.
  • The defaults could be improved, esp. clustered.
  • Support for data attributes in the layout would be useful for the concentric (circular) and clustered layouts.
  • Etc.

Add basic GAL filtered debug menu

• This menu item replaces the current network with GAL-filtered. It's useful for debugging/testing.

Also updated eslint to make unused variables warnings rather than errors. We may have to customise this more in future, as we're mostly just using preset rules.

[maxkfranz]

@mikekucera, since you're working on the feature/design-photo-ed branch, merge this in whenever it's convenient for you

[maxkfranz]

@mikekucera @chrtannus @d2fong @jingjingbic I've cherry-picked the CI fixes to master so your future PRs should be green now