Project modernization & some fixes

[rsyring]

• Coppy and related modernization
• JavaScript: remove the date time polyfill
• Fix imports when openpyxl isn't present (No openpyxl throws error #189)
• Rendering: fix paging_select() input display (Page number input box is not on the same line with it's "of count" #190)
• Fix translations (Fix translations #194)
• Move to GH CI

[codecov]

Codecov Report

❌ Patch coverage is 96.45062% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.49%. Comparing base (e884310) to head (816fba6).
⚠️ Report is 54 commits behind head on master.

Files with missing lines	Patch %	Lines
src/webgrid/testing.py	75.75%	7 Missing and 1 partial ⚠️
src/webgrid/blazeweb.py	0.00%	4 Missing ⚠️
src/webgrid/filters.py	94.87%	4 Missing ⚠️
tests/webgrid_tests/test_columns.py	40.00%	3 Missing ⚠️
src/webgrid/renderers.py	96.72%	2 Missing ⚠️
src/webgrid/validators.py	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #198      +/-   ##
==========================================
+ Coverage   89.81%   95.49%   +5.67%     
==========================================
  Files          26       18       -8     
  Lines        6303     6014     -289     
  Branches      523      395     -128     
==========================================
+ Hits         5661     5743      +82     
+ Misses        557      187     -370     
+ Partials       85       84       -1     

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