diging/amphora: Release v0.6

Release notes - Amphora - Version v0.6 Bug [JARS-84] - Users who are not added to a public collection can't see public collections in Vogon [JARS-88] - celery_start script needs to start one process for celery beat and an extra for workers [JARS-96] - Resources don't seem to follow public/non public rules Story [JARS-80] - Github token authentication should cache Github responses [JARS-83] - There should be a functionality to define where the content of a resource starts and ends [JARS-90] - support resource content uploads through REST API [JARS-92] - Resource type field needs to be an autocomplete field [JARS-93] - Adding/editing metadata: predicate field needs to be an autocomplete field [JARS-95] - It should be possible to restart a Giles upload that failed before.