Add "Placeholder" text option to form field management

[FuelAgency]

At present field "Label" and "Placeholder" are identical on the front end and inherit the Label value in Formulate, or if blank, the Name.

Ideally, these could be managed separately so information is not always duplicated and the Placeholder text can be specified completely separately if desired.

For this reason, it would be great to add a "Placeholder text" field to relevant field types in Formulate. It could fall back to Label and Name if left blank, thus not upsetting existing forms after upgrade.

Discussion started here (with visuals) https://our.umbraco.com/packages/backoffice-extensions/formulate/formulate-questions/89273-how-to-use-name-above-field

[Nicholas-Westby]

This approach makes sense to me. If you or somebody would like to submit a pull request, I would welcome it.

I assume we're talking about the plain JavaScript template (rather than the AngularJS template).

[FuelAgency]

We use the "Responsive" template.
There are two options offered:

• Responsive
• Responsive (JavaScript)

We've had trouble implementing the "JavaScript" one and use the other.
Perhaps the selection interface should specify "Responsive (AngularJS)" to help differentiate?