Missing PhET-iO elements in Preferences dialog under simPreferences

[pixelzoom]

Related to #140 (add support for dynamic locale), I'm running into a problem with the Preferences dialog in Studio. The sim adds one subpanel that contains a title ("Dipole direction") and a radio button group:

The subpanel is implemented in DipoleDirectionControl.js, the radio button group in DipoleDirectionRadioButtonGroup.js.

After opening the Preferences dialog, under moleculePolarity.general.view.navigationBar.preferencesButton.preferencesDialogCapsule.preferencesDialog.preferencesPanels.generalPreferencesPanel.simPreferences you'll see this subtree:

Four problems, all in DipoleDirectionRadioButtonGroup.js:

(1) DerivedProperty negativeToPositiveRadioButton.negativeToPositiveStringProperty is missing from the tree.

(2) negativeToPositiveRadioButton.labelText is missing child textProperty that links to negativeToPositiveRadioButton.negativeToPositiveStringProperty.

(3) Similar to (1), DerivedProperty positiveToNegativeRadioButton.positiveToNegativeStringProperty is missing from the tree.

(4) Similar to (2), positiveToNegativeRadioButton.labelText is missing child textProperty that links to positiveToNegativeRadioButton.positiveToNegativeStringProperty.

Am I hitting some limitation/problem with PhetioCapsule?

[pixelzoom]

I thought the problem might be caused by instantiating DerivedProperty inside of a dynamic component. So I temporarily moved negativeToPositiveStringProperty and positiveToNegativeStringProperty to MPConstants. The behavior was unchanged.

[samreid]

Fixed in the commit, please review. Also, should we convert StringUtils to TypeScript and ban certain keys/value types? But perhaps this will be better addressed in PatternStringProperty which @jonathanolson is working on.

[pixelzoom]

Fixed in the commit, please review.

Oh duh, options in the wrong place... and thanks.

Also, should we convert StringUtils to TypeScript and ban certain keys/value types?

I don't think that's necessary. If Molecule Polarity had been in TypeScript (it is now), this would have been caught.

Closing.