add healthy and fearless [effect]s

so we don't have to these these traits specialy.
cleanup 'generate_description' flag.

'generate_description' is now a normal flag that defaults to true, this
is simpler to understand than the previous way.
update changelog
Merge pull request #253 from gfgtdf/traits_effects

add healthy and fearless [effect]s

so we don't have to treat these traits specialy.