Made Entity an abstract class

Added lots of features :)
Update Entity.java
Fix build errors (Travis CI)
Temp fix for Class not Found. Read description

org.vizun.world.Location can not be found because vLib is not included in pom.xml
Should we make another Location class or will vLib be part of the client?
Merge pull request #13 from Xesau/patch-1

Entity changed to Abstract class & added functionality