Minor class name inconsistencies

I read through the commit for #2374637: Prefix classes with commonly used names, like content, sidebar, header, footer?:

http://cgit.drupalcode.org/radix_layouts/commit/?id=4b99d06

... and found some minor inconsistencies:

• radix_bartlett still had "content-header" and put the "radix-layouts-contentheader" on a different element than radix_bartlett_flipped
• radix_bartlett_flipped wrapped the content columns in "radix-layouts-content" which didn't match radix_barlett and it seems this was dropped from all the other layouts
• radix_sanderson had all the columns as "radix-layouts-sidebar" whereas radix_sanderson_flipped had individual classes for each column
• radix_selby had a similar problem to radix_barlett where the "header" class was still present and "radix-layouts-contentheader" was on the wrong element

I'll attach a patch to fix in a moment!