Add option to disable nests with low nest spawn counts

[comstud]

Some stuff from nc:

 echo "update nests set discarded=NULL where pokemon_avg >= $nest_min_spawn_hr and active=1 and discarded = 'spawnhr_warn';" >&3
 echo "update nests set discarded='spawnhr_ban', active=0, pokemon_id=NULL, pokemon_form=NULL where pokemon_avg < $nest_min_spawn_hr and active=1 and discarded = 'spawnhr_warn';" >&3
 echo "update nests set discarded='spawnhr_warn' where pokemon_avg < $nest_min_spawn_hr and active=1 and (discarded <> 'spawnhr_ban' or discarded is NULL);" >&3