class library: use only QT GUI classes.

This is a rather large refactoring that removes all redirects which were introduced to allow to switch between different GUI kits (such as cocoa, swing and QT) at runtime. This ability was useful, but made the system very complicated and inefficient (This change speeds up Pen by 100 %).

This refactoring leaves intact old syntax insofar as (e.g.) GUI.slider still works, also QSlider can be used. Slider should be used directly now (this has been standard for a while, but there are still other cases around). In the folder GUI/backwardsCompatibility there are redirects for the classes prefixed by Q.

I changed all classes from QSomething to Something wherever there was already a direct access in such a way. More QT specific classes lile QPalette kept their Q-prefix.

The implClass functionaliyt was removed, but it is kept intact in the help system in case in the future someone wants to use class name redirects for something.

Also Stethoscope and FreqScopeWindow (and related classes) needed a change, they now keep the server as an instance variable instead of initialising a global server at startup.

Some helpfiles still need to be adjusted.

Thanks to Jakob Leben for very useful hints.
scide: change label: show node tree
help: improve example in help file
class libary: adjust helpfile names
class library: GUI: completing replacement of QView by View
class library: GUI: removing PlusFreqScope redirects
class library: GUI: updating helpfile
class library: GUI: updating helpfile
class library: GUI: prperly deprecating drawHook instead of just removing it.
class library: GUI: improve backward compatibility of FreqScope
help: GUI: update help file name
class library: GUI: new folder hierarchy

This commit reorders the GUI files according to what made sense to me.
class library: GUI: use Pen class directly.
help: improve plotter example to show specs better