Add voting handler

[ansgarS]

Is your feature request related to a problem? Please describe.
The bistro server should provide a possibility to manage menu votes.

Describe the solution you'd like
The following routes have to be served:

PUT /voting/<MenuId> { rating: Float }
RETURNS { userRating: Float, communityRating: float }

GET /voting/<MenuId>
RETURNS { userRating: Float, communityRating: float }

Describe alternatives you've considered
Not yet.

Additional context
None