Add avandu-tt-rss-api-level command

This command gets the api level from tt-rss, this doesn't serve any
purpose yet, but it could be used later-on to determine which features
are and aren't available.

avandu.el

@@ -397,6 +397,18 @@ feeds."
   (interactive)
   (avandu--next-button-of-type backward feed))
 
+(defun avandu-tt-rss-api-level ()
+  "Get the API level of the your Tiny Tiny RSS instance."
+  (interactive)
+  (let ((level (cdr (assq 'level
+                          (assq 'content
+                                (avandu--send-command
+                                 '((op . "getApiLevel"))))))))
+    (when (called-interactively-p 'any)
+      (message "API Level: %d" level))
+
+    level))
+
 ;; Overview
 (define-derived-mode avandu-overview-mode special-mode "Avandu:Overview"
   "Major mode fo the avandu overview screen.

doc/avandu.texinfo

@@ -241,3 +241,15 @@ the session variable that was returned by the api.
 Log out of the Tiny Tiny RSS instance, reset the session id, username
 and password used by avandu.
 @end deffn
+
+@deffn Command avandu-tt-rss-api-level
+Request the api level of the Tiny Tiny RSS instance.  If called
+interactively in any way it will print a message like:
+
+@example
+API Level: #
+@end example
+
+This does not currently serve any purpose, but it might be used in the
+future to determine which functions are available.
+@end deffn