Evaluation for users who introduce new ratings

Wrote an evaluation method that introduces new ratings for a user and
measures how recommendation improves as a user introduces these new
ratings. This evaluation isolates the users ratings, and does not add
any ratings besides one user’s ratings.
Added time context evaluation and cleaned up code

Added a new evaluation for evaluating recommender systems within a time
context as users add new preferences. Also cleaned up code and got rid
of old evaluation methods.
Fixed the MysqlDataSource singleton

Acts a singleton to retrieve pooled connections to a MySQL database
Added endpoint to add ratings for a movie

User can add rating using Rating data access object and MovieResource
Added new evaluation to introduce non-target data

New evaluation that adds non target user data to the training data
model and evaluates on part of target user’s future data. Shows the
relationship between recommendation improvement and increased training
data
MetricSystem singleton
Merge branch 'master' of https://github.com/pcas00/movie-recommender-service