fix to LinePlaneIntersection function

- (u+v)<=1 would only allow an intersection of the triangle p0/p1/p2

Signed-off-by: Thorsten Liebig <Thorsten.Liebig@gmx.de>
operator: additional fix to FindPath

Signed-off-by: Thorsten Liebig <Thorsten.Liebig@gmx.de>
useful: use own matrix determinant and invert instead of vtkMatrix3x3

The only reason for this is that vtkMatrix3x3 would require vtk > v5.4

Signed-off-by: Thorsten Liebig <Thorsten.Liebig@gmx.de>
Merge remote-tracking branch 'dac/master'
FF plots: doc updates and some error/warnings added
update news for upcoming release

Signed-off-by: Thorsten Liebig <Thorsten.Liebig@gmx.de>
matlab: use xticklabel with num2str for octave compatibility
matlab: add warning for gnuplot colorbar issue