Added user & model manager test

mozen/src/main/java/mozen/business/IModelManager.java

mozen/src/main/java/mozen/business/IUserManager.java

mozen/src/main/java/mozen/business/ModelManager.java

mozen/src/main/java/mozen/business/UserManager.java

mozen/src/main/java/mozen/web/ModelController.java

mozen/src/test/java/mozen/business/ModelManagerTest.java

mozen/src/test/java/mozen/business/UserManagerTest.java

mozen/src/test/java/mozen/repos/UserRepositoryTest.java