Improved sniffer rule of I-O-M files.

The "keyword" at the start of I-O-M files has changed some
time ago. Now sniffing for both possibilities.
Corrected typo in overwrite alert.
Updated WebPositiveBookmarks optional package

Changed a few icons so they're not all the same...
Added a link to the "Community links" on the website.
Corrected type from hrev46630. Sorry...