Adds a non-endpoint specific page to the API documentation about
organization-level roles and permissions for users in order to
highlight important and useful information for clients and API
users.
Also, adds links to new documentation page in related areas
of the API documentation.
We change the title to be more descriptive and also link to the
overall Zulip changelog, since one can reasonably get to this page
when googling for "Zulip changelog".
I imagine this can be improved in various ways, but I've initialized
this with all the **Changes** entries recorded in either zulip.yaml or
the rest of the API documentation, and I expect we'll be able to
iterate on this effectively.
It'll also be useful as a record of changes that we should remember to
document the API documentation as we document more endpoints that
currently don't discuss these issues.
While working on this, I fixed various issues where feature levels
could be mentioned or endpoints didn't properly document changes.
Lists API client bindings/libraries/wrappers and makes a distinction
between official core projects and community projects.
Tweaked by tabbott to sort the community and outdated libraries, and
restructure how we talk about other projects.
Fixes#2093.