Add 3D effective area to the specs

[TarekHC]

Hi all,

I have two main motivations to add a aeff_3d to the specs. and also support within science tools (3D: ENERGY, DETX and DETY):

• In MAGIC, as we only have two telescopes, the acceptance is not radially symmetric.
• If we want to reach the extremely low systematic uncertainty levels of CTA, we definitely need to add the zenith angle dependence within the FoV. For example, if the whole array is pointing 50deg away from zenith, and the whole FoV cover ~9 deg, then there will be a clear difference between the effective area between the top and bottom edges of the field of view (even if the offset is equal).

It shouldn't be a lot of effort to include this neither to the specs nor the science tools. What do you think, would it make sense? I could work on it 2/3 weeks from now.

Cheers!