change css cleaner and site style to prevent work skin styling breaking out of work container
add caller_check option to css_cleaner clean method to allow work skin to exclude position:fixed; change selector prefixing regex to prevent styling of the parent element via sneaky selectors
use prefix regex when checking for allowed properties; remove comment-handling logic which would eat whole rulesets if it  found comments inside rulesets; remove prefixed properties from allowed properties lists in config; update skin creation help file with tips about parser behaviour and new tutorial
add public skins liink to help file; generalize note about duplicate declarations
fix #workskin prefixing