Add configurable block placement event simulation

Mods can override ItemBlock onItemUse/placeBlockAt, which bypasses
Bukkit's normal block placement codepath. The Bukkit BlockPlaceEvent
can be instead sent in World canPlaceEntityOnSide to cope with the
world protection bypass, however, the temporary block placement
can cause duplicate item drops with certain mods.

To support both situations, until something better can be developed,
the simulation is now configurable with the following new settings in
bukkit.yml's mcpc section:

simulate-block-place-event-IDs: a list of block IDs to whitelist/blacklist

simulate-block-place-event-default: a boolean, either:
 true: enable event simulation, except for block IDs listed above
 false: disable event simulation, except for block IDs listed above

These settings let you choose sending-events/not-duping, as appropriate:

- If you are seeing dupe item drops on block place, disable simulation
- If you are not getting block placement events, enable simulation