Current color scheme picker design is hard to extend

[melchoyce]

The color scheme picker design is nice for only a handful of schemes, but adding new themes makes it feel unwieldy and forces users to scroll.

[ryelle]

26336.diff​ removes the dropdown styles & switches color scheme list to 26336.png​. This just changes the look, functionality is all the same.

[ryelle]

26336.2.diff​ adds styling for responsive, dropping from 3 to 2 columns of options on <600px.

[nacin]

Do these color scheme representations make sense as tables?

[azaozz]

Not sure if the number of colors in $color_info->colors is always 4. If yes, no need for tables there. Divs or spans with inline-block and width: 25% would work just as good.

Also ​line 573 is not needed after the patch.

We do ksort() of the available color schemes there, not sure why. Seems the Default (a.k.a. 'fresh') should always be at the top.

[azaozz]

In 26336.3.diff:

• Pulled the default (fresh) option to always be first.
• Changed the structural CSS to inline-block, no float.
• Reduced the padding a bit.

[azaozz]

In 26506:

Improve the admin color scheme picker:

• Easier to extend.
• Remove the "drop-down" look, show all choices inline.
• Some PHP and JS cleanup.

Props ryelle, fixes #26336.