Entity hexadecimal color support

Hi Nicolas,

First of all, thank you very much for your awesome work on AndEngine.

I just add two new methods on org.andengine.entity.Entity and org.andengine.entity.IEntity to let people use hexadecimal colors this way : 
sprite.setColor(0xc5bb46);

Modifications on :
org.andengine.entity.Entity
org.andengine.entity.IEntity 

setColor(final int pHexValue);
setColor(final int pHexValue, final float pAlpha);

Thank you in advance and have a good day ! :)

Tony Beltramelli
Multimedia developer

www.tonybeltramelli.com