Handle error messages for elipse fitting

Created by: sebherbert

Currently throwing ugly warning messages in the Matlab GUI. To be handled properly

Warning: Gauss-Newton did not converge, returning linear estimate In fitellipse (line 113) In surface3D_combine>BioCellEllipseFitting (line 946) In surface3D_combine>allDimEllipseFitting (line 792) In surface3D_combine>cell2ellipse (line 782) In surface3D_combine (line 143)

Warning: Ellipse is near-circular - nonlinear fit may not succeed In fitellipse>fitnonlinear/sys (line 254) In fitellipse>fitnonlinear (line 214) In fitellipse (line 109) In surface3D_combine>BioCellEllipseFitting (line 946) In surface3D_combine>allDimEllipseFitting (line 792) In surface3D_combine>cell2ellipse (line 782) In surface3D_combine (line 143) `