mergeField does not merge two QStringLists correctly

If appman is provided with several configurations, it is supposed to merge the configuration files, resulting in a new configuration.

For parameters like ui.importPaths the result should be a list of all defined import paths from both configurations.

However, currently it will only use the ui.importPaths list from the latter of the two configuration files.

This happens because ui.importPaths is a QStringList and the best overload match of mergeField would be:

template <typename T> void mergeField(T &into, const T &from, const T &def)
{
 if (from != def)
 into = from;
}

The same result would happen for every other QStringList in the configuration.