Fetch stream values from graphql #68
This implementation is a bit of a hack, however doing this the right way (pulling the DATA_SOURCES into the DataStore) is quite a lot of effort because the constants.DATA_SOURCES is being used promiscuously in the code-base. I spent about an hour cleaning this up but it ended up being a reasonably large change (i.e., technical risk) so that it's worth doing this temporary hack for now.
There currently is a bug in the data: the pipelinekey in Cassandra is all-lowercase like "twitter" but the frontend assumes that it's capitalized like "Twitter". This issue will take care of itself once we update the streams table in Cassandra. More generally speaking, I had to edit quite a few of the columns in the streams table... we should start paying attention to that table and insert proper values into it instead of dummy values.