SciDAVis - Improvements SVN-temp

- replaced Qwt4.2 with Qwt5 (snapshot from 2006/01/30)
- disabled most of the Qwt based functionality for now in order
to make QtiPlot compile with Qwt5 (!This means all plotting
functionality is broken now!)
reason: Port to Qwt5 is a lot harder than I thought, too many
changes in the API and the class structure
result: QtiPlot compiles and starts without errors
(Plan: Port the trunk to Qt4 now and port/enable the plotting
stuff afterwards.)