Colour / color themes.

[willwade]

• Document / list hex codes for themes in v5
• Create a way of changing your colours by changing a theme in v6. Note this is not for the config / overall UI - just dasher zooming pane and elements.

As a dasher user I'm used to changing colours of the zooming interface by selecting a color theme. This is useful because some of these themes have been in existence a long time - but also some of these themes feel easier particularly for dasher novices.

[willwade]

Colours can all be found here: https://github.com/dasher-project/dasher/tree/master/Data/colours