Convert ScriptParameter choices field to text from charfield

[Chris7]

User had a lot of choices, and there is no real reason to limit this field.

[codecov-commenter]

Codecov Report

Merging #351 (c661659) into master (a5099df) will decrease coverage by 20.39%.
The diff coverage is 25.00%.

@@             Coverage Diff             @@
##           master     #351       +/-   ##
===========================================
- Coverage   72.93%   52.54%   -20.40%     
===========================================
  Files          38       51       +13     
  Lines        2398     3340      +942     
  Branches      356      545      +189     
===========================================
+ Hits         1749     1755        +6     
- Misses        530     1469      +939     
+ Partials      119      116        -3     

Flag	Coverage Δ
unittests	52.51% <25.00%> (-20.43%)	⬇️

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Impacted Files	Coverage Δ
wooey/tests/test_views.py	0.00% <0.00%> (ø)
wooey/models/core.py	79.90% <100.00%> (ø)
wooey/tests/mixins.py	0.00% <0.00%> (ø)
wooey/tests/test_tasks.py	0.00% <0.00%> (ø)
wooey/tests/test_template_tags.py	0.00% <0.00%> (ø)
wooey/tests/factories.py	0.00% <0.00%> (ø)
wooey/tests/test_commands.py	0.00% <0.00%> (ø)
wooey/tests/__init__.py	0.00% <0.00%> (ø)
wooey/tests/config.py	0.00% <0.00%> (ø)
wooey/tests/test_utils.py	0.00% <0.00%> (ø)
... and 7 more

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