Add ref, source and utm_source as referrer

[BetaHuhn]

Backend implementation to fix #169

[BetaHuhn]

I am having trouble figuring out how to change the URL scalar to a union in the GraphQL API as I am not ver familiar with this. Also currently the UI displays an error as it expects the referrer id to be a URL not a string,

[coveralls]

Pull Request Test Coverage Report for Build 640

• 9 of 15 (60.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 45.0%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/aggregations/aggregateNewFields.js	3	4	75.0%
src/aggregations/aggregateRecentFields.js	3	4	75.0%
src/aggregations/aggregateTopFields.js	3	4	75.0%
src/database/referrers.js	0	3	0.0%

Totals
Change from base Build 635:	-0.3%
Covered Lines:	434
Relevant Lines:	767

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 639

• 9 of 15 (60.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 45.155%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/aggregations/aggregateNewFields.js	3	4	75.0%
src/aggregations/aggregateRecentFields.js	3	4	75.0%
src/aggregations/aggregateTopFields.js	3	4	75.0%
src/database/referrers.js	0	3	0.0%

Totals
Change from base Build 635:	-0.1%
Covered Lines:	434
Relevant Lines:	767

---

💛 - Coveralls

[electerious]

Thanks 👍 Please let me know when the two comments are resolved. I will merge it into a dedicated branch and add the GraphQL part tomorrow so you can continue with ackee-track if you want.

[electerious]

Resolved the issues. The union idea didn't work out. I've adjusted the GraphQL schema to return a String for the referrer id. It now needs a isUrl function in the UI to detect URLs (the currently list only works with URLs).

[BetaHuhn]

electerious/ackee-tracker#27 adds support for this feature to the tracker.