Functional tests check propogation of data

Added func test for tiered fetch against Datastore

Updated & normalized formatting
Utilize DataBlobFactory to generate test data

Utilized DataBlobFactory for test data generation

Created a helper class to generate test data

Added developer note
Added server-side error codes
Implementing ScoreSource

Implemented ScoreSource
Mocked service for urlfetch

Added helper container UrlFetchBlob

MockService implements UrlFetchBlob

Cut out unused code from UrlFetch mock service
Added ScoreSource to the Chain-of-Responsibility

Implemented ScoreSource into workflow