BUG: reference editor createNew only handles hardcoded title property but not custom one

[mhsdesign]

As seen here in the code

neos-ui/packages/neos-ui-editors/src/Editors/Reference/createNew.js

Line 38 in 4d1baf9

const titleProperty = this.props.options.createNew.titleProperty || 'title';

or shown by this issue #1764

the createNew option allows to redirect the entered title in a custom property field if titleProperty: 'myTitle' is used. But with the introduction of the node creation handlers, https://github.com/neos/neos-ui/pull/422/ not all data/elements were saved as node properties. Currently only showInCreationDialog: true(promoted properties) or thetitle` property is automagically saved.

See pr #2563 where we hardcoded the actual default value of titleProperty.

We should instead, if we want to support the feature, transmit

createNewData:
  titleProperty: title
  value: fhiewofiewnfoewjf