Beautify the messages when importing tickets

[bschmalhofer]

Currently the output looks like:

reading file tickets_25aa//tickets_25a000007.csv.

Import of 110 Ticket records:
---------------------------------------------------------------------
Success: 110 succeeded
Error: 0 failed.
Import of 110 Ticket records: 100 Article created
Import of 110 Ticket records: 10 Ticket created
Import complete.

Nice to have:

• show the chunk count
• Success: 110 succeeded is not really informative
• First show ticket stats, then article stats
• add stats for attachments
• Sum up in the end
• Computer readable output, maybe JSON