SciDAVis - Improvements SVN-temp

- Added installation script for the nullsoft scriptable installation system
(http://nsis.sourceforge.net). Contributed by Mauricio Troviano, with some
details changed:
- changed compressor from "lzma" to "/SOLID lzma" (for a smaller installer)
- adjusted output filename to be consistent with other released files
- removed Qt debug libs (not needed if Qwt, QwtPlot3D and Qtiplot are all
built in release mod)
- removed qwt5.dll (Qwt is linked statically by default)
- removed requirements.txt (we need a different solution for the installer;
offering to download Python and PyQt installers would be favourite)
- removed plugins\*.a (static plugins make no sense)