Fire PlayerInteractEvent on client + more changes

[copygirl]

This pull request makes PlayerInteractEvent more consistent and useful, mostly making the event available on the client. The following changes are included:

• PlayerInteractEvent fires on the client.
  • Cancelling the event on the client will prevent packets from being sent to the server.
  • Setting useItem to DENY on the client will make blocks appear unbreakable.
• Setting useItem to ALLOW will allow blocks to be broken even in adventure mode.
• Right clicking air without an item will send a packet to the server, causing a right click air event.
• Left click block will fire regardless of game mode, as long as the block isn't broken instantly.

And as a little added bonus:

• Added "documentation" to PlayerInteractEvent.
• Fires PlayerDestroyItemEvent on client too when item is used up in onItemUseFirst.
• Current item is not wrongly set to null on client if the passed item has a stack size of 0, even though the current item was set to a new stack.