onTradeAccept event

Now is fine :)
Merge pull request #931 from dalkon/master

Add optional safety checks for addEvent
Small updates and aditions to items.xml
More fixes and aditions
Merge pull request #932 from EPuncker/master

Small updates and aditions to items.xml
Small improvment to isPremium function
removed parentheses
Merge pull request #933 from EPuncker/master

Small improvment to isPremium function
Fix crash when trying to remove inexistent node in WildcardTree

Fixes #935
Fix #926
Fix in onTradeAccept

If return false trade will be canceled
Merge pull request #894 from djayk1/master

onTradeAccept event
Change return type of internalCloseTrade from bool to void