MarkItUp! editor and some bbcode fixes

Here is a pile of good intentions. It probably breaks every convention you ever wanted to follow, but it is a working bbcode editor, with the current tagset.

The worst part is where I write JS in php with heredoc syntax. I didn't want any of it to load if there is no form, but I could have added it to an external file instead. The reason why I did it is the `{$form->FormName()}` variable, but in hindsight I could have just targeted the textarea and the button directly.

Also there is a list implementation which can lead to breaking html if some is able to slip a `[*]` to an attribute, but luckily it is not possible currently with our tagset. This will surely need some improvents, but JBB is not very good with unary tags. That is why I haven't added the buttons to the editor. Yet.

There *are* decent parts though.

More info in the commit messages.