New functions for TroubleTicketSystem

- Attachments
To add an attachment to a ticket, a group tts has to be created and every user,
who works with tts has to be in that group.

- New field "Type"
If Setup works correctly, the subcategories needed schould be created. If not,
create a global (under admin->admin, not admin->tts) category called "tts" and
a subcategory called "type". Every
subcategory added under "type" will then appear in the field.

- New field "Platform"
Same as "Type", with "platform" being a subcategory of "tts".

- New field "Effort"
It's just a string ;-)

- Auto-Filters
There are dropdown-boxes for "category", "assigned to", "created by" and "priority".
Choose any entry from the boxes and the list of tickets will be filtered.

