use get_value

same as field::add_card

correspond to apply_field_effect and cancel_field_effect

face down card cannot activate effect generally
硫酸のたまった落とし穴  is not special now

* new trap monster rule

* new ruling of special summon once

* new ruling of (special) summon count in oath

* new ruling of trigger effect

trigger effect cannot be activated if the card is moved to other place

* update (extra) deck effect handling

including new rule that effect of face down card in extra deck cannot be activated unless explicitly written

* new trap monster rule: changing to face down

* new trap monster rule: disabled

* fix changing to face down of trap monster

close #293

if the target is self destroyed, it should not count in the return value

except in field::process

round decimals correctly in scripts
close #264