Camerahub

* Make table headings in detail views be anchors and links. Add icons to table headings (485)
* Improve validation of shutter speeds. Apply formatting in the ShutterSpeed model so we can get rid of the template tags (486)
* Drop image circle for fixed lenses (498)
* Add separate fields for fastest and slowest shutter, rather than tracking every single shutter speed (499)
* Add date imprint to camera model (500)
* Drop created/updated fields now we have proper history (501)
* Improve note about PC sync (502)

* Fix error 500 when updating a lens model (495)

* Format apertures as _f_/8 and shutter speeds as ¹/125 (486)
* Automatically calculate angle of view for lens models, provided we know the focal length and the film format diagonal (488)
* Denote colour/B&W filmstocks with relevant icons, not just booleans (490)
* Drop rectilinear field as the information is already captured by other fields, e.g. lens type (491)

* Track lens type based on angle of view (481)
* Replace embedded lists with a link to a filtered list (479)

* Fix Error 500 when listing negative sizes (461)
* Move camera & lens images to the top of the page (473)
* Order negative sizes alphabetically (475)

* Fix error when creating a cameramodel with no metering (464)
* Include a field for self-timer (466)
* Display number of objects in all list views (467)
* Tag field is now hidden when empty (468)