Updated berkshelf to 3.1.5

Updated berkshelf from 2.0.18 to 3.1.5 in Gemfile and added supermarket
source to Berksfile

Change-Id: I4b52e73be3e7db4afd142a6e80b844d667599d8b
Implements: blueprint update-berkshelf
Merge "Updated berkshelf to 3.1.5"