The new built in Rating field in CB 2.0 can already do some of that. You'd configure it as follows for example.
Rating Step: 0.5 (allows half stars)
Force Whole Numbers: Disable (shuts off rounding)
Regarding displaying the numerical value no that's not implemented, but yes I can add that.
The below is what it looks like with half star, display of numerical rating, and display of votes.