* Extract field value (beamline, proposal number and proposal type) from the
* data json object. Returns null if the field is not found.
*
* @param {array}
* subject The array containing objects of interest template
* @param {string}
* field The text field which is searched
* @param {array} subject The array containing objects of interest template
* @param {string} field The text field which is searched
* @returns {array} the found field in an array. When the field is string composed of coma separated items, each item is returned in the array. When there is no text, an empty array is returned