Ability to search users

[Toastbrot236]

This PR does the following:

• Makes the level search category also include matching users in its responses for games
• Adds a separate user search category for APIv3
• Makes level search no longer include levels by users with matching name (since searching users themselves is possible now)
• Allows level category game responses to include users

Needs unit tests and real tests, otherwise I think it's done.

Closes #997.