Unquote the quoted data from XML file when reading. We don't want quoted chars to be visible in the GUI.
XML report format 1 only had error "lines" that we promoted to "items" when adding to GUI. XML report format 2 contains error "items" so change the code to read items and do the promotion directly when reading and parsing the data.
Fixes ticket #2543 (GUI: Xml report does not quote special characters)
A base class is needed for e.g. some common routines that can be shared between the formats.
Kimmo Varis