- change the parent: KPlotWidget is now only a QWidget and not also a QFrame

- change the parent: KPlotWidget is now only a QWidget and not also a QFrame
- reworked a bit how the KPlotAxis are handled; a QHash of their type stores
  them, use axis() to get a pointer to an axis
- add a nice way to show a tooltip of the current point object under the cursor;
  it's a property and freely toggleable
- move some setter method as slots
- use fmod (in <math.h>) instead of dmod (in KPlotWidget itself) and deprecate
  the latter
- fix the drawing of grid
- apidox fixes

svn path=/trunk/KDE/kdeedu/libkdeedu/; revision=493271