Format update errors more nicely

Right now the update error string has \n characters in it. However these seem to get eaten somewhere along the line, so the whole string is rendered as one giant unreadable blob of text. Also it is not semantically correct to use \n characters for newlines interspersed with other formatting tags in the same string, so let's convert them to <nl/> tags which KUIT formatting will automatically transform into appropriate HTML tags for us.

RFC because currently the QString::replace(QLatin1String("\n"), QLatin1String("<nl/>")) function call undesirably and automatically converts <nl/> into <nl/>, which obviously does not work. :) And I can't figure out why it's doing this or how to make it not do it.

Assistance fixing this would be appreciated.