Some blocks, such as beds, doors, or flowers, are actually composed of
multiple blocks when they are placed. Currently, to detect how many
blocks are actually modified a plugin has to perform various calculations
to determine the directions of relative blocks, many of which are
difficult to perform and can easily return false positives.
This commit adds in a BlockMultiPlaceEvent, which adds in easy support for
accessing all blocks modified by the placement of a block.
By: Nate Mortensen <nate.richard.mortensen@gmail.com>