Author: Roland Hafner?

Provides a general interface for user input.
Clients can connect to the GUI server via TCP/IP.
The program can be initialized through sending a request string
that describes the UI element to be generated.
It will report the state of the element to the client on demand.

Currently, the only available UI element is a slider, which is
requested through the string
  SLIDER <label> <minimum> <maximum> <initial> <steps>


Known bugs:
On some systems, the QT-Slider widget does not function
properly, but keeps snapping to certain values. There is
no known fix for this at present, though the issue can
be worked around to some degree by changing the values
in the parameter gui_request_string in cartpole_gui.cls,
which should cause different locking positions.
