Add getting an identifier by obj

Signed-off-by: Chris Sanders <zidane@outlook.com>
Adding entity/player event interfaces

Adding a base event interface for both `Entity` and `Player`
Ignore .nb-gradle folder
Add collection of online players, max number of players, and a getPlayer method to `Game`
Add Damageable class with basic methods
Add AsyncPlayerChatEvent
Updating Block event with reference to Voxel

Updated `BlockEvent` with `Voxel getVoxel()` for block/position. I'm debating
renaming the events to `VoxelEvent` but that may be too different from
what devs are accustomed to.