Optionize max vertices for buffer operator

[navis]

Not a big deal but somtimes default max vertices (96) makes too huge polygon than expected.

[stolstov]

@navis In the OperatorBuffer, the third execute method is missing the public keyword: abstract GeometryCursor execute(GeometryCursor input_geometries, SpatialReference sr, double[] distances, double max_deviation, int max_vertices_in_full_circle, boolean b_union, ProgressTracker progress_tracker);

Add the "public" there instead of these changes. Would this work for you?