Camerahub

* Add support for fixed-lens cameras (307)
* Fix pagination issues (308)
* Improvements to detail views (310, 311)

* Display camera and lens model disambiguations in list view (267)
* Fix display of focal length and angle of view (283)
* Improve elements/groups display (285)
* Remodel lens coating as a multi choice field (287)
* Fixed mount displays as boolean icon (290)
* Add mirror lock-up (291)
* Drop coupled metering (297)

* Ensure constraints have unique names (295)

* Implement friendly URLs (slugs) for several public data types (286)

Dummy release to test CI/CD

* Build Docker images in Travis and push to Docker Hub (255)
* Test migrations as part of CI pipeline (255)
* Show related camera and lens models for mounts (248)
* Add x-sync speed to cameramodel (240)
* Add dynamic filters and filter forms for most list views with django-filter (233, 266)
* Make handling of tables more explicit (233, 266)
* Use django-filter to take over static filters where private objects are only visible to their owner (233, 266)
* Remove tonable property of paperstocks (265)
* Multiple choice for paperstock finish (270)
* Multiple choice for battery chemistry (268)
* Model compatible batteries
* Add responsive hamburger menu to nav bar (230)
* Filters are public data, modelled as types rather than specific filters (262)