Mongo DB Updates for OpsWorks and Amazon Linux Support

This is the mongo db support from edelight, but with a working instance for a custom Amazon Linux OpsWorks layer. As of testing, the OpsWorks support for a single instance is now working, and the instructions are included in an updated readme file in the root of the repo. The main changes that got the single node instance working involve making changes to the chef script that allow it to work with chef 9, the addition of the mongod.conf template for the service to work correctly with Amazon Linux, and the addition of the journal path link creation to point to the journal volume instead of just having mongo create it in the data volume (this is outlined in the Mongo DB docs regarding EC2 setup for Mongo DB). Any other code changes from the edelight version are likely cosmetic. The only other addition from the edelight version is the recipe that removes the 10gen repo (see readme for details).