SciDAVis - Improvements SVN-temp

a window to a folder and than removing that folder.
- Fixed a crash in Graph::insertCurvesList() occuring when the list of columns
to plot includes invalid entries (e.g. due to a mistake when plotting from
Python).
- Added enum QwtPlot::Axis to the Python API. API functions working on axes
expect the axis to be given as an integer corresponding to values of this
enum; and using the numbers directly is hard to read and write.