Extract constants
Add "sensor" to entity listener

This needs to be done so that all information about the contact is known
in an entity listener. Previously, the listener had no information about
*which* fixture on the entity was being contacted.
Fix error caused by previous commit
Rename variables to be more clear

LoserContactListener no longer only deals with Sensors, so the names of
the contacting fixtures have been changed to reflect this.

EntityListener just had flat out wrong names
Make processFixture public

So that it may be called manually instead of beginContact or endContact,
which requires a Contact object
Change visibility of LoserContactListener to protected

Player needs to access it in order to fix its contacts when it turns its
alternate bodies off
Let player fix its contacts whenever its body is switched

The Player class switches bodies internally, which keeps endContact from
being called. endContact isn't called when a body is set to inactive.
Therefore, Player needs to manually manage a list of its contacts and
call processFixture (begin = false) whenever it switches bodies. 

Note, this commit does not call the method to flush contacts yet
Move anonymous class to private nested class PlayerContactFixerListener

Needed in order to call the method to flush the leftover contacts from
within Player
Flush contacts when Player switches bodies internally

See 302824054f53dc893dd39b139c0b2a42dd8b49ab for an explanation of why
this is needed
Double bugfix

flushContacts didn't actually notify the object that the player was
contacting that the contacts had finished, so that needed to be done.

also fixed an array unpacking error
Merge pull request #13 from SweatyReptile/develop

Various improvements and bugfixes (Player flushBodies fix)