Changed rounding for intrinsic growth rate display

Added "elements_Leslie" function

Also corrected some Q_marks

Added button "calibrer vr"

Corrected dimension stuff in pop_proj for 2-age classes situations
Added cv_env = 0 for fast_paced species

corrected calibration inside DD models

clean error msg for expert elicitation (part "capacité de charge" only ; still need to do the other ones)

Avoids potential weirds offsets btw "avg trend" and "CI of trend"