Improve QLoggingCategory example code in documentation

Don't use a qt.* category in the user documentation: These should be
reserved to Qt internal use, and also have special semantics (QtDebugMsg
by default off) that might lead to confusion.

Also, adapt the camel case naming convention for logging categories
defined by the macros. This was the (although somewhat controversial)
result of a recent discussion on the development mailing list.

Change-Id: Ic7162b47bb2d76550c766bc40dd65ce039e7e3eb
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Fix current directory setting in manual dialog test.

It was always constructing a QUrl from the string causing the warning
"Non-native QFileDialog supports only local files" with the
new QUrl-based implementations of getOpenFileUrl(), etc.

Change-Id: Idd9bb432a48865df137f8f39f53014dda150ffe9
Reviewed-by: David Faure <david.faure@kdab.com>
Remove outdated comment

Change-Id: I4d662318acf072ce9cbfd9c024f5316a0617f2e6
Reviewed-by: David Faure <david.faure@kdab.com>