Improve load before operation of rest api.

[sara-02]

Currently this loading creates the graph every time the rest api comes up, we can pre-process and store it in S3. Will require a new endpoint to train and store.
https://github.com/fabric8-analytics/fabric8-analytics-license-analysis/blob/master/src/rest_api.py#L24

[tisnik]

@sara-02 are you planning to add this issue to Planner and to the current sprint?