closes #2998 without unnecessary code to implement another feature (the goal can be fully reproduced in onHear now)

unified sendCreatureSay so speaker == spectator check is not necessary anymore

onCreatureHear is now a boolean

same convention as in talkactions:

• return true - the character line is displayed for the spectator
• return false - it doesn't - creature:say(...) can now be used instead, to send a different message (return false has to be used after onSay events within onHear to prevent overflow)