Display the default limit for daily requests on the API admin page

[katska]

Problem we're trying to solve
Admins wanting clarity of the API limit for each API user.

Background
Currently the number of API calls given isn't shown on the admin interface API admin page ... If not shown on each admin page where the limit can be changed, then show a link to a page where this information can be seen - associated with #1877 wanting clarity of the API limit for each API user.