mod_incidents_handling: recommit after full test, cleaned it a bit as what I posted was regretfully an unfinished draft, replaced a lot of the fixed type fields used for fields description with desc elements (upstream prosody's util.dataforms will still strip those). Also moved auxiliary functions to a library.

2c07bcf56a36d6e74dc0f5422e89bd61f4d31239 0.8-diverge