Add event checkin functionality, seperate power tests into a different form (#536)

* Split power related parts of event checklist into a seperate form

* Revamp H&S overview, remove individual lists.

They were not a good thing.

* Remove old 'vehicle/crew' stuff

* Very initial version of checkin form

* Further work on checkin, add role field etc

* Fix tests after form split

* Add ability to edit checkins, more validation

* Basic checkin/out logic complete

* Add homepage checkin for events happening now

* Minor improvement to homepage UI

* Checkin button turns into checkout button where applicable

* UI work

* Clicking check out does not redirect the user

* Register check in model with the admin site

* Add power record status chip, checklist status chip displays number of checklists

* Minor fixes

* Implement codedoctor suggestions

* pep8

* Add data migration for crew/vehicles

* Checkin only requires login (no perms) and block users from editing other checkins at Django level

RIGS/templates/partials/ec_power_info.html

@@ -47,6 +47,6 @@
                 </tr>
             </tbody>
         </table>
-        <p><strong>Voltage Drop on Circuit:</strong> 5% (approx. 12v)</p>
+        <p><strong>Voltage Drop on Circuit:</strong> &#8804;5% (approx. 12v)</p>
     </div>
 </div>