moved getTalk/setTalk from RatingService to new PresentationService
renamed TalkController -> PresentationController
renamed talk variable to presentation; changed display of average rating
per presentation
reformatted code
some style improvements
added date functionality to comments (broken)
show and format timestamp in comments
fixed creation of a Date object in JSON format
Merge pull request #54 from SchweizerischeBundesbahnen/feature/mwa/commentStyling

Feature/mwa/comment styling
Merge branch 'develop' into feature/mfr/rating