Consistent colour values. Settings icon colour.

Changed the CSS colour values to be consistent (uppercase, full
definition).

Changed the settings icon for the dark/nightfall theme to be more
visible.
Simplified changeTheme function.

Simplified the change theme function. Now it doesn't refresh the page
when the theme is changed. (tested in chrome)..
Colour full definition values.

Missed out some of the other colour definitions. Now all CSS files
conform to this.
Merge pull request #4 from JamieSharpe/master

Consistent colour values. Settings icon colour. Simplified ChangeTheme function