Make API pagination size configurable

Description

Currently the per_page parameter for API pagination defaults to 20 and can be set to a maximum of 100. The spirit of this limit was to help with performance, by restricting very large queries. However, there are many specific cases in which requesting a very large number of items are actually more performant than many small queries.

Proposal

• In the Admin settings, add a setting that reflects the per_page setting, with a configurable value
• In the Admin settings, add option to allow a per_page flag to be passed as a parameter on individual requests

UX should determine right place in admin settings hierarchy to put this. Potentially under /admin/application_settings/network/#User and IP Rate Limits