Fixed wrong displaying of \'e type accents

In tag 03N8 the code \text{\'e made the parser barf. Given my newly
written "look for contexts in which accents are used" code I should do
the same for all possible accents and check their parsing.
Less padding in menu because it became too wide in certain browsers
Fixed removal of remaining \label{}'s

In tag 06B3 a \label{} wasn't being removed because it was at the end of
the line, made the newline (which is necessary to fix paragraph
formatting if I remember correctly) optional
Items and equations now refer to containing tag

The tag page for an item or equation now contains a link to the parent
tag, so it's actually possible to directly navigate to the containing
tag.
Fixed escaping and URLs in math mode

It now applies to *all* math mode, and the parsing of URLs is fixed too
Remove \linebreak[0]

In tag 06ER the \linebreak[0] command was used, but MathJax doesn't know
it, so we get rid of it
Fixed parsing of \href{}{} with email adresses

Tag 06RG is an example of this