add metamethod to get the length of Group (#136)
add metamethod to get the length of Group (#136)

so now we could use #g instead of Group.GetCount to simplify the scripts
Fluorohydride/ygopro-core,DailyShana/ygopro-core,mercury233/ygopro-core,DailyShana/ygopro-core,nekrozar/ygopro-core,nekrozar/ygopro-core,Fluorohydride/ygopro-core,mercury233/ygopro-core