Ui tweaks

[MikeJohnPage]

• Updated title font to match BRC branding
• Added custom grey frame. Arguably, it is against our branding guidelins to have such a heavy use of the colour red (it should be used for accents). In my opinion the old theme was too noisey, and the excess of colour detracted from the graphs.
• Rejigged the layout so all plots are now in tabs, improving the space available for the map.
• Rejigged the sidebar instructions and layout (e.g., padding, fonts, etc.) to improve the UX.

[MikeJohnPage]

I updated the Dockerfile but can't remember if anything else needs updating for adding the dashboardthemes package.