#417 More ESCET dark theme support

Plot visualizer:

• Plot visualizer does not need to store theme listener is a field.

CIF simulator GUI input component:

• JavaDocs are more clear about background vs foreground colors.
• Added light and dark theme color schemes and theming support.
• Color composites are now color canvases.
  • Setting background color for a component doesn't work.
  • Eclipse dark themes overrides it.
  • So is now a canvas that is manually painted.
  • To allow (re)painting, store color choices in field choiceColors.
• Added focus listeners to ensure colors 'stick' when using dark theme.
• Improved color markers.
  • Previously they were color composites, now color canvases.
  • Made them a bit wider, to be better visible.
• Updated CIF simulator documentation.

Addresses #417 (closed)