Api tweaks

[Scarecrow0w]

Hello. Could you please extend API:

1. Extend route /api/users with fields param, so we could provide fields to be only included in the response. It would be much lightweighter query if I want to get only username and data_limit field
2. Extend route /api/users/reset with usernames param, so we could provide resetable usernames array|json. Because it's not convienent to reset users 1 by 1 if I don't need to reset them all. I could need to reset 150/200 users and it would be much easier to do this with 1 query instead of 150