Fix bug with invalid utf8-characters.

Prior messages containing invalid utf8-characters were inserted
into the database only until the first occurence of an invalid
character. Now this character will just be removed and the rest
will be inserted normally.
Make it possible to mark text in the message view.

The messageView will now only be closable using a newly
introduced X in the top right corner of the view instead
of anywhere in the text. This makes it possible to mark
text inside the view.
Mark text matching rules inside messageView.

Now inside the messageView text that matches the rules is
hightlighted. This means now it is highlighted WHY a message
is classified as bad.