Moved Event Manager component to separate package

Author: Majkl578

composer.json

@@ -19,7 +19,8 @@
         "doctrine/cache": "^1.0",
         "doctrine/collections": "^1.0",
         "doctrine/lexer": "^1.0",
-        "doctrine/annotations": "^1.0"
+        "doctrine/annotations": "^1.0",
+        "doctrine/event-manager": "^1.0@dev"
     },
     "require-dev": {
         "phpunit/phpunit": "^6.3",