color schemes: disable barbie, 80's and lioness color schemes; minor code cleanup

git-svn-id: https://plugins.svn.wordpress.org/mp6/trunk@764816 b8457f37-d9ea-0310-8a92-e5e31aec5664
color schemes: corrected `line-height` of new color picker dropdown arrow

git-svn-id: https://plugins.svn.wordpress.org/mp6/trunk@764817 b8457f37-d9ea-0310-8a92-e5e31aec5664