Trigger subsonicupdate on db_change and splupdate

- Trigger subsonicupdate on database_change event instead of only at import
  event.
- Send a new event from smartplaylist plugin whenever lists are updated/created
  and have subsonicupdate plugin listen to it.
- Make sure the both events register a new listener that launches the actual
  subsonic library update at the very end of a beets run (cli_exit) instead of
  during each change (similar to how mpdupdate plugin does it).

beetsplug/smartplaylist.py

@@ -17,6 +17,7 @@
 
 
 from beets.plugins import BeetsPlugin
+from beets.plugins import send as send_event
 from beets import ui
 from beets.util import (mkdirall, normpath, sanitize_path, syspath,
                         bytestring_path, path_as_posix, displayable_path)
@@ -232,6 +233,8 @@ class SmartPlaylistPlugin(BeetsPlugin):
                         if self.config['urlencode']:
                             path = bytestring_path(pathname2url(path))
                         f.write(prefix + path + b'\n')
+            # Send an event when playlists were updated.
+            send_event("smartplaylist_update")
 
         if pretend:
             self._log.info("Displayed results for {0} playlists",

beetsplug/subsonicupdate.py

@@ -53,7 +53,14 @@ class SubsonicUpdate(BeetsPlugin):
             'auth': 'token',
         })
         config['subsonic']['pass'].redact = True
-        self.register_listener('import', self.start_scan)
+        self.register_listener('database_change', self.db_change)
+        self.register_listener('smartplaylist_update', self.spl_update)
+
+    def db_change(self, lib, model):
+        self.register_listener('cli_exit', self.start_scan)
+
+    def spl_update(self):
+        self.register_listener('cli_exit', self.start_scan)
 
     @staticmethod
     def __create_token():