Ranking groups

[JoeyRubas]

closes #481. Generalized way to manage special ranking groups, like ESL speakers, debaters with no highschool experience etc. Sort of a niche feature, but ESL was requested and it seems better to create a generalized solution that can be used for anything of this nature, having ESL and EFL (foriegn language) at the same tournament is pretty common in BP for example

[codecov]

Codecov Report

❌ Patch coverage is 91.33333% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.54%. Comparing base (45be0d5) to head (3ec34c4).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
mittab/apps/tab/views/views.py	73.07%	7 Missing ⚠️
mittab/apps/tab/forms.py	81.48%	5 Missing ⚠️
mittab/apps/tab/models.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #485      +/-   ##
==========================================
+ Coverage   76.36%   76.54%   +0.17%     
==========================================
  Files         111      114       +3     
  Lines        8111     8254     +143     
==========================================
+ Hits         6194     6318     +124     
- Misses       1917     1936      +19     

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