Revision: Undo unsafe change to TLuaInterpreter::clearRoomUserData()

Extending the functionality as the previous commit did left the risk that a
new script would unintentionally delete additional room user data if used on
a previous version of Mudlet.  Additional functionality has been transferred
to new command TLuaInterpreter::clearRoomUserDataItem( roomId, key ) and the
original command reverted to previous action - though retaining the addition
of returning a Boolean value to indicate whether any data WAS deleted.

Signed-off-by: Stephen Lyons <slysven@virginmedia.com>