Event: move validation to annotation and add UniqueEntity constraint on Participation

src/Bundle/ChillEventBundle/config/validation.yaml

@@ -1,26 +0,0 @@
-Chill\EventBundle\Entity\Participation:
-    properties:
-        event: 
-            - NotNull: ~
-        status:
-            - NotNull: ~
-        person:
-            - NotNull: ~
-    constraints:
-        - Callback: isConsistent
-        
-       
-Chill\EventBundle\Entity\Event:
-    properties:
-        name:
-            - Length:
-                min: 3
-                max: 75
-                minMessage: The event name must have at least {{ limit }} characters.
-                maxMessage: The event name must have maximum {{ limit }} characters.
-        type:
-            - NotNull: ~
-        circle:
-            - NotNull: ~
-        center:
-            - NotNull: ~