Enhancements for ERProfiling

[darkv]

This patch include several enhancements for ERProfiling:

• the doctype tag and any HTML comments won't get a class attribute anymore (future enhancement could be to exclude all tags that don't allow a class attribute)
• use CSS outline instead of border in order to not "destroy" your HTML layout as border will change either dimensions of element (box-sizing: content-box) or content (box-sizing: border-box)
• check if a tag already has a class attribute (former implementation looked up only first attribute, leading to tags with two class attributes which is not allowed and will formally delete the second one thus removing CSS classes you probably need…)