Lots of little cleanup things

[cycomachead]

See #172

• do not store access/refresh tokens on login
• fix changing a teacher's school
• show admin users on the teachers index
• refactor schools index
• show pages sidebar on the dashboard
• allow editing/deleting a school directly
• cleanup a bunch of logic around selectize/school forms
• remove some old db columns
• rename the db columns on pages
• lots of little code cleanup

[cycomachead]

Test cases to add:

• [ ] test admins on Teachers#index
• test teacher#edit shows the right school by default
• ensure teacher#edit can update the right school
• smoke+auth tests for schools #new, #index, #edit
• ensure schools#show has the correct teachers count / list of teachers
• explicit test case for changing a teacher's school (controller specs)

[codecov]

Codecov Report

Base: 95.28% // Head: 86.43% // Decreases project coverage by -8.85% ⚠️

Coverage data is based on head (8ddab67) compared to base (28e16d5).
Patch coverage: 81.37% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #175      +/-   ##
==========================================
- Coverage   95.28%   86.43%   -8.86%     
==========================================
  Files          18       18              
  Lines         509      538      +29     
==========================================
- Hits          485      465      -20     
- Misses         24       73      +49     

Impacted Files	Coverage Δ
app/controllers/schools_controller.rb	70.00% <54.83%> (-26.16%)	⬇️
app/controllers/teachers_controller.rb	96.18% <89.13%> (-2.05%)	⬇️
app/controllers/application_controller.rb	100.00% <100.00%> (ø)
app/controllers/main_controller.rb	100.00% <100.00%> (ø)
app/controllers/pages_controller.rb	97.82% <100.00%> (ø)
app/controllers/sessions_controller.rb	100.00% <100.00%> (ø)
app/models/page.rb	100.00% <100.00%> (+3.84%)	⬆️
app/models/school.rb	91.48% <100.00%> (+2.12%)	⬆️
app/models/teacher.rb	85.24% <100.00%> (-0.24%)	⬇️
lib/csv_process.rb	15.21% <0.00%> (-73.92%)	⬇️
... and 1 more

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