Improve "All submissions" view

[murhum1]

Currently the new "All submissions" view is very slow, on courses with only 500 submissions taking ~10sec to load. Figure out why and improve it.

Related: #1409

[ihalaij1]

PR #1449 improves the performance of the page, but pagination should still be added to make the page usability better.

[mikaelGusse]

One thing to note is that you cannot use the filters if you are in the default "Show only 50" submissions view. This would be quite crucial to get working.

Another suggestion from Otto was to make it so that you could use URL get parameter to filter the page so e.g. https://minus.cs.aalto.fi/aplus-manual/master/teachers/all-submissions/?status=Error. Would show all submission with Error status.