Add 'id' attribute to h2 elements in the wiki

[dmurphy25@…]

By adding the 'id' attribute to the h* elements in the wiki, it would be possible to link to both a page and a specific section of the page.

e.g.

== Versions ==

…would become…

<h2 id="versions">Versions</h2>

… and could be linked to with [wiki:SomePage#versions].

It would also need to correct case/replace spaces with underscores in both the tag generation and link parsing.