Fixes bug 895928 Adding signature_summary* matviews:
* Add signature_summary* tables to PostgreSQL model
* Add update_signature_summary() and backfill_signature_summary()
* Update backfill_matviews()
* Add crontabber job and enable in defaults
Merge pull request #1359 from selenamarie/bug895928-signature-summary-to-UDF

Bug895928 signature summary to udf