Generate Incidence Angle maps

S1Tiling is able to generate Local Incidence (LIA) maps on each tiles and orbits.

This issue propose to generate also Incidence Angle (IA) map, which correspond to the incidence angle on the ellipsoid.

These IA maps will be used to transform sigma0 to gamma0 or beta0 products using these relationships:

sigma0 = beta0.sin(IA)

gamma0 = beta0.tan(IA)