The old constructor treated the string argument either as filename or
as raw XML data, depending on 2nd parameter. This is a mess and quickly
leads to confusion.
Now we have two constructors taking either a filename as string or a
QByteArray with XML data. Loading actual data has been separated into
MultimediaProject::loadData( const QByteArray & ).
Signed-off-by: Tobias Doerffel <tobias.doerffel@gmail.com>