SciDAVis - Improvements SVN-temp

- Improved drawing of scale tics in 2D plots.

- Splitted "fitclasse" into several new files and removed it from SVN.

Implemented Feature Request #3307: Integrate functions in Plots.

- Fixed printing of Pie plots.
- Fixed exporting to vector formats for 3D et 2D plots. Added the PS format as an export option.
- Added an export to PDF action button.
- Fixed bugs in FitDialog.
- Fixed bug in reading recent project files list from user settings.

- hopefully found the best solution for the problem
described in rev 412
- fixed crash in differentiation function

- Implemented saving/restoring of antialiasing settings for individual graphs.
- Improved drawing of ErrorBars and of Bar curves (still not perfect!).
- Moved some of the content in fitclasses to two new files: ExponentialFit and MultiPeakFit (.cpp and .h). Should we do the same for all the other fit classes?

- Fixed restoring of backup files and added an open menu entry for these files.
- Fixed bug in adding error bars.
- Got rid of superfluous "activeGraph" pointer in ApplicationWindow. Modified some functions accordingly (especially the DataSetDialog).

Fixed bugs in changing plot associations for 2D plots.

- fixed loading of spline curves
- fixed loading of project files from version 0.7.8
(I don't know if it works for versions >0.7.8
and <0.8.3 since I don't have the code of those old
versions. The important question is: When were the 2 lines

if (style <= LineSymbols || style == Box)
s+=QString::number(symbol.pen().width())+"\t";

added to Graph::saveCurveLayout(int index).
This decides the first part of the condition
in lines 10165 and 10179 in ApplicationWindow.cpp.)

- Fixes restoring of curve axes for ErrorBars.