feat(auth): implemented users and user auth

#5 [Story] Create User Sessions

knockoutwhistweb/app/logic/user/UserManager.scala

@@ -0,0 +1,10 @@
+package logic.user
+
+trait UserManager {
+
+  def addUser(name: String, password: String): Boolean
+  def authenticate(name: String, password: String): Boolean
+  def userExists(name: String): Boolean
+  def removeUser(name: String): Boolean
+
+}