FFT: improved to deal with NaN data
merge_proj: corrected to reproduce dt if unique
uvmat.fig: tooltip corrected
plot_field: bug for isocontour corrected,
im_filter: cleaning
phys_polar: spatial derivative included (still to check)
set_obeject.fig: minor correction
struct2nc: comments improved
uvmat: button NB implemented
read_civxdata: error message improved