Default page size for reading sites when opening the configurations page

When we currently open the configuration pages the frontend requests the sites from the backend for both filtering & later for assigning the configurations to sites.

This doesn't have an explicit page[size] parameter, which means that it stops with 30 sites (and doesn't contain more then that).

It would be useful to add an page[size]=10000 parameter to the request, so that we can be sure that we load them all.