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"

+ small Q_popover modifs

and : "Intensité" instead of "Force"

and "tendance locale..." by "tendance pop"

Test on 10 scenarios !

+ some minor eolpop-package cleaning

Set Env. Variance at 8% ==> SD ~28%

(it works!)

We don't include newborns (age class 1) into the population count.

(+ small correctionsnin shiny)