Fix inherited readonly props

[ehennestad]

Motivation

Some schema attributes are redefined to be readonly for inherited classes. In MATLAB a property attribute can not be redefined for subclasses, so it was possible to set readonly properties.

How to test the behavior?

es = types.core.ElectricalSeries()
es.data_unit = 'volt' % works
es.data_unit = 'millivolts' % should not work

Checklist

• Have you ensured the PR description clearly describes the problem and solutions?
• Have you checked to ensure that there aren't other open or previously closed Pull Requests for the same change?
• If this PR fixes an issue, is the first line of the PR description fix #XX where XX is the issue number?

[lawrence-mbf]

@ehennestad This is not kosher but could you apply the fix mentioned in here: #262 (comment) as most of the errors in these tests come from there.

[ehennestad]

The failed test is actually a good sign!

Error using types.core/ElectricalSeries/validate_data_unit
Unable to set the 'data_unit' property of class '<a href="matlab:doc
types.core.ElectricalSeries">ElectricalSeries</a>' because it is read-only.

[lawrence-mbf]

lgtm

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (9d77234) 88.49% compared to head (d8d18f0) 88.52%.

Files	Patch %	Lines
+file/fillValidators.m	95.83%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #560      +/-   ##
==========================================
+ Coverage   88.49%   88.52%   +0.02%     
==========================================
  Files         104      104              
  Lines        4616     4636      +20     
==========================================
+ Hits         4085     4104      +19     
- Misses        531      532       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.