Add "Item" suffix to Solute combo box items

[pixelzoom]

Over in phetsims/sun#615, it was decided that elements in a group should still have a tandem name that indicates their type.

In pH Scale, the combo box items under soluteComboBox.listBox should all have an "Item" suffix. Doing this by concatenating "Item" onto the solute tandemName is OK.

TODO list:

• add "Item" suffix in SoluteComboBox.js
• update any ids that appear in overrides.js
• update ph-scale client guides
• update ph-scale-basics client guides
• cherry pick to ph-scale 1.4
• cherry-pick to ph-scale-basics 1.4
• cherry-pick common-code changes that enforce "Item" suffix

[pixelzoom]

@arouinfar please review the changes to the client guides for ph-scale and ph-scale-basics. They have been pushed to master, ph-scale 1.4, and ph-scale-basics 1.4. If they look OK, you can unassign yourself and reassigned to me. Thanks.

[pixelzoom]

ComboBoxItem change is phetsims/sun@187ac98 and has been cherry-picked to ph-scale 1.4 and ph-scale-basics 1.4.

[pixelzoom]

Cherry-picked phetsims/sun@55c4fc0, which improves the error message for the assertion in ComboBoxItem.

[arouinfar]

@pixelzoom the changes are all looking good in master. I reviewed the tree, client guides, and checked that relevant elements remained phetioFeatured.

[pixelzoom]

Ready for testing in next RC. To verify:

1. Run the sim in Studio
2. Verify that all of the combo box items under phScale.macroScreen.view.soluteComboBox.listBox have a name that ends with "Item". E.g. "batteryAcidItem".
3. (ph-scale only) Verify that all of the combo box items under phScale.microScreen.view.soluteComboBox.listBox have a name that ends with "Item". E.g. "batteryAcidItem".

[KatieWoe]

Win 10 Chrome 1.5.0-dev.1 #195 (comment) looks ok. Closing