UI: Config form: Adding widget to assist the user on filling the properties

[shral]

If the user needs to add some properties, for example like IID_PATIENT_URL or STOWWebApp etc, while configuring the WebApp it would be good to get a dropdown with all valid parameters.

[gunterze]

Another option we may think about is to move configuration from general WebApp properties, to particular attributes of a UIWebApp child object in the UI configuration tree, referenced by the WebApp name (dcmWebAppName).

[vrindanayak]

Web Application Properties are independent of UI using a specific web application or not, even though agree that web apps were introduced for our UI. For eg. w.r.t. STOWWebApp specific property pointing to STOW_RS web application (used by CD Import function) is essentially nowhere displayed for usage by UI at all.

Currently this issue is more about providing easy-to-add properties using a widget wherever dcmProperty is used in other parts of configuration schemas in the archive (eg. exporter / export rule / storage etc.). As part of fulfilling #4027 the web application properties are now seen and select-able in other configuration schemas, which is misleading.

Also, uiWebApp.schema.json describes itself as Web App drop-down list which means it is not limited to one web app and is intended for serving some other purpose. I vote for renaming / updating uiWebApp.schema.json to indicate its real intended use instead.