Add editorial column and filtering

[Riolku]

The problem page now has an editorial column. The search form can now be
used to only show problems with an editorial.

The only extraneous change is adding a method to Problem,
has_public_editorial.

Here's some screenshots of the UI I get locally:

Editorial Column, plus sorting:

Filtering:

[codecov-commenter]

Codecov Report

Merging #1844 (7316268) into master (0516433) will decrease coverage by 0.04%.
The diff coverage is 28.57%.

@@            Coverage Diff             @@
##           master    #1844      +/-   ##
==========================================
- Coverage   46.09%   46.05%   -0.05%     
==========================================
  Files         224      226       +2     
  Lines       12876    12933      +57     
==========================================
+ Hits         5935     5956      +21     
- Misses       6941     6977      +36     

Impacted Files	Coverage Δ
judge/views/problem.py	24.29% <28.57%> (-0.25%)	⬇️
judge/admin/submission.py	44.32% <0.00%> (-0.94%)	⬇️
judge/admin/contest.py	44.39% <0.00%> (-0.39%)	⬇️
judge/admin/problem.py	56.86% <0.00%> (-0.38%)	⬇️
judge/utils/problem_data.py	15.62% <0.00%> (-0.20%)	⬇️
judge/views/contests.py	29.60% <0.00%> (ø)
judge/views/api/api_v2.py	47.79% <0.00%> (ø)
judge/views/submission.py	32.17% <0.00%> (ø)
judge/bridge/judge_list.py	0.00% <0.00%> (ø)
... and 6 more

---

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[Riolku]

Fixed casing thanks to Xyene, refer to updated image for the casing on the search form.

[Riolku]

Here are screenshots showing what happens when other editorial situations arise.

[Riolku]

Sorting was removed entirely. has_public_editorial, as a method, was also removed, because it is no longer called.

retracting

[Xyene]

Can avoid the extra class since you're already tagging with an attribute

Suggested change

	.has-editorial-color {
	td[editorial=1] i {

[Xyene]

But w/e, the rest of the code is written like this already so sure