Enhancement: Added more attributes to itemlist

Added/Updated attributes in class.itemlist.php:
* added the real tech level
* renamed old tech level to metalevel
* added item volume
* added item mass

Thanks to sparky41 for this update!
Fix: CrestParser, NPC kills and permanent deletion

Fixed an issue with the Crest Parser calculating a wrong kill hash for
kills with faction NPCs as involved party, possibly resulting in an SQL
error.

Also fixed an issue when trying to post permanently deleted kills via
CREST, works now correctly.
Enhancement: Added "ignore NPC kills" option to IDFeed

Added a separate "ignore NPC kills" option to IDFeed.
Can be configured in ACP -> Feed Syndication (section "Options").
IDFeed class now distinguishes between API import and IDFeed and uses the
appropriate configuration setting.