Requested by Alan from Julich.

Iframes extractor and previewer such that:

-JSON files containing URLs together with other metadata are sent to an extractor.
-Extractor validates the JSON. If JSON is invalid it returns a message to the server that JSON is invalid.
-If JSON is valid, extractor extracts the URL and returns it to the webserver to be previewed using iframe.
-Rest of the metadata in JSON are uploaded as file "technical" (need to change this wording now) in Medici, connected with the file.
-In addition to showing the iframe, the previewer also checks the file upload date with current date, and if more than a set time has passed, shows a message to users with Edit rights to review the file (to check if URL is still alive).