Color theme step 2

* Added new section in header.php that injects the color scheme
* Added various color handling and color conversion functions to
frontendediting; converting rgb to hex, and rgb to hsl values
* Added conversion routine to darken or lightne colors based on
lightning %
* Added new section to fly out menu, used to configure primary color of
color scheme. Note that only the middle color is working; the lighter
and darker "versions" are derived based on a percentage entered in a
configurable textbox. Values can already be stored.
* CSS is injected "on the fly"