Add database APIs to query tickets

[abitmore]

Add APIs:

• list_tickets( optional_limit, optional_start_id )
• get_tickets_by_account( account_id_or_name, optional_limit, optional_start_id )

[sschiessl-bcp]

Should tickets be part of full accounts?

[abitmore]

On one hand, all objects should be added to full accounts so more info is available via one API call.
On the other hand, the get_full_accounts API is already very heavy and is abused IIRC (which leads to lagging).
Let's revisit the topic later.