Search for any type of file in admin tool

Currently it was just searching for `.yaml`, but now the script allows
for any type of extension.
Decode htmlspecialchars from comments when displayed in admin tool

This prevents any sort of `<script>` injection from activating inside
the admin tool.
Increase the default number of comments displayed per page

This makes my workflow of spam hunting easier.
Search for any type of file in `admin/blacklist.php`

There was one place I forgot to fix what I had fixed earlier.
Trim preceeding or trailing invalid characters from resulting file name
added dynamic message-id to email headers
Merge branch 'dev'