Refactor all api_key code to project_api_key

[Twixes]

Even after #32 there's a ton of api_key param usage, which is confusing, because there's personal_api_key too AND project_api_key is the replacement that works in most relevant places. However we should move to supporting the latter two exclusively (including in internal code), removing ambiguous api_key completely or only maintaining minimum simple support to avoid breaking most existing user setups.