Fix CSS multiple selectors rules

Hi!

I fixed a bug: when a CSS rules are multiple selector, only the first one was prefixed with the demonstration element id.

I took the opportunity to renamed variables:
 * allCode => codeElementList
 * code => codeElement
 * val => cssRules
 * style => styleElement

 I also tried to improve syntax consistency:
 * space before brackets
 * space after statement

Cheers,
Thomas.