Start creating the Qt UI

This is based on several commits from Tomaz - mingled together and mildly
extended by Dirk (mostly Makefile hacking).

All Qt UI related stuff should eventually move into the qt-ui directory.
So the Makefile rules for moc and uic have been adjusted accordingly.

The MainWindow class has been moved into its own file in qt-ui (but just
with a placeholder, the existing class has simply been ifdef'ed out in
qt-gui.cpp for the moment).

We still have a couple of Qt things in qt-gui.cpp in the main directory...
all this needs to move into the qt-ui directory and be built with separate
.h files. Right now we have the one-off Makefile rule to create the
qt-gui.moc file from the qt-gui.cpp file.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>