pfSense/pfsense e0bd07fsrc/usr/local/www/widgets/widgets picture.widget.php

Picture widget corrections. Fixes #9610

* Sanitize user input before using as path/filenames
* Use a more accurate method of determining image type on read
* More sanity checks before reading images.

(cherry picked from commit 2c544ac61ce98f716d50b8e5961d7dfba66804b5)
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+34-9src/usr/local/www/widgets/widgets/picture.widget.php
+34-91 files

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