AllocationsTable: Support theming

[ajmas]

Currently the AllocationsTable component uses the US allocations table colours and can't easily be modified.

The current values are in the src/utils/FrequencyUtils.ts file.

Three possible approaches:

• Moving the definitions to a CSS file, with a theme prefix for each colour and allow the theme to be overridden by a theme name property
• Providing a theme property with a JSON with 'servicename -> colour' map
• A hybrid of the two

Right now I am leaning toward the third option, just for flexibility. Open to discussion.

Note, any values in the CSS or table that contain spaces or characters unfriendly to CSS should be normalised to be CSS friendly.