Implemented phantom buildings.

Phantom buildings are buildings that aren't built, but can be seen so
that they can be placed when built. They will hover under the mouse, and
orient itself depending on a nearby building.
Phantom created on build command.

When a build towncenter command is click while the villager is selected,
a phantom of the towncenter will appear. This phantom will disappear if
the user right clicks.
Buildings can be placed but not correctly.

Phantom buildings, when left clicked close to another building, can be
built, but they are not placed in the correct location yet.
Buildings can now be built in a proper location
Merge pull request #28 from Jbtyson/master

Adding the ability to build buildings.
Merge pull request #29 from Jbtyson/buildings

Buildings can now be built!