Rating microservice persistence implemented and dockerized

Changes made:

• Repository implementation changed and JPA used.

• Repository methods are tested.

• Integration test for find by ID functionality implemented.

• Rating, movie and user ID type switched to UUID.

• Unit tests are all modified because of type change.

• Rating microservice dockerized and connected to database.

• IMPORTANT: This PR should not be merged before !15 (merged) since it implements connection to postgres docker database.