pfSense/pfsense ce5ea3csrc/etc/inc util.inc, src/usr/local/www services_captiveportal.php

Image upload validation improvements. Fixes #9804

* Make functions for validating images against a pre-defined list of
approved types
* Change the picture widget to use these functions
* Add validation for uploaded Captive Portal logo/background images

(cherry picked from commit 09d597434c9ccb456c8f207649dbe43fd5ff85db)
DeltaFile
+6-21src/usr/local/www/widgets/widgets/picture.widget.php
+21-0src/etc/inc/util.inc
+13-4src/usr/local/www/services_captiveportal.php
+40-253 files

UnifiedSplitRaw