[B+C]Implementation of improved block targeting system. Adds BUKKIT-5581

#### Implementation of improved block targeting system. Adds BUKKIT-5581

##### The Issue:
See https://github.com/Bukkit/Bukkit/pull/1059 for detailed information.

##### Justification for this PR:
See https://github.com/Bukkit/Bukkit/pull/1059 for detailed information.

##### PR Breakdown:

The following changes are made:

* New methods are added to CraftLivingEntity to implement the new API in Bukkit LivingEntity class.  Several private helper methods have also been added.
* Implementation of ``Vector[] getHitbox()`` has been added to CraftBlock
 
##### Testing Results and Materials:

Source: https://github.com/desht/testplugin
Binary: https://dl.dropboxusercontent.com/u/12467600/targetblock-test.jar

See https://github.com/Bukkit/Bukkit/pull/1059 for instructions on use.

##### Relevant PR(s): 
 
B-1059 - https://github.com/Bukkit/Bukkit/pull/1059 - Related Bukkit PR
 
##### JIRA Ticket: 
BUKKIT-5581 - https://bukkit.atlassian.net/browse/BUKKIT-5581
C comes before J which should also be in it's own section.

```
import com...

import java....

import net....

import org...
```