SciDAVis - Improvements SVN-temp

- added muParser to the windows installation instructions

- improved the readme file (mainly the windows compilation instructions)

- muParser removed from 3rdparty; it is now installed separately like most other libs.
- Miscellaneous scripting-related bits fixed.

Several adjustments to the build system. Unix defaults are consistent with the installation instructions again.

- moved the fit operations into a sub menu "quick fit"
- some minor fixes

- did some code cleanup
- added doxygen documentation to FitDialog

- some more improvements to the project file

- some corrections in scidavis.pro

- edited the project files and split them into
several files to make them more concise and
make it easier to use a custom project file

- unified the context menus for the title bar and the
project explorer as suggested by Knut
(the related code still needs a lot of cleaning up after
release 0.1.0)