Corrected typo in "skins-wizard-forground-color"
Changed text slightly to make it clearer that it is a percentage of the
browser's default font size.
Added a note to say this only applies to site skins and inviting the
user to use the Work Skins button for new work skins.
Amended text at the top of the wizard and added a link to create a new
works skin.
Merge pull request #764 from ariana-paris/Issue_2699-Skins_help

Issue 2699 skins help