Custom Component Colors

We are going to need to have at least some custom component colors. This gives more flexibility but makes each theme customisation more complex.

Current custom values:

The feature needs a special gradient overlay, customised to the theme

• feature-overlay-gradient

The main menu highlight colours seem to require their own specific color values

• menu-highlight-primary
• menu-highlight-secondary
• menu-highlight-tertiary

Footer colors

• footer-color
• footer-background-color

Progress bar colours

• progressbar-0 - color at start of progress bar
• progressbar-100 - color at start of progress bar

$detail-panel-bg - work out if needed specifically or can use a generic colour?