[pinterest] improve PinterestAPI code; remove OAuth mentions

on another note: access_tokens have been set to only allow for
10 requests per hour (from 200 yesterday)

docs/configuration.rst

@@ -820,13 +820,26 @@ How To
 =========== =====
 
 
+extractor.pinterest.access-token
+--------------------------------
+=========== =====
+Type        ``string``
+How To      - register a Pinterest application and use its client-id and
+              client-secret (see `extractor.pinterest.client-id & .secret`_)
+            - run `gallery-dl oauth:pinterest` and authenticate access with
+              (preferably) the same account that registered the application
+Notes       Access tokens currently only allow for 10 requests per hour.
+=========== =====
+
+
 extractor.pinterest.client-id & .secret
 ---------------------------------------
 =========== =====
 Type        ``string``
 How To      - login and visit Pinterest's
               `Apps <https://developers.pinterest.com/apps/>`__ section
-            - click "Create app"
+            - agree to "Pinterest Developer Terms and the API Policy"
+              and click "Create app"
             - choose a random name and description and click "Create"
             - scroll down and set a Site URL (e.g. https://example.org/)
               and allow https://mikf.github.io/gallery-dl/oauth-redirect.html