Rename Sud's Download/Upload to Save/Load throughout

Renames everywhere the concept appears: Sud.download()/upload() ->
save()/load(), the 'Download'/'Upload' websocket messages ->
'Save'/'Load', the brewpi_gui menu actions, handlers and
sud_download_path -> sud_save_path, and the demo script. Behavior is
unchanged - this is naming only, from the client's perspective (save
to / load from a local file) rather than the server's.

components/sud.py

@@ -63,7 +63,7 @@ class Sud(AttributeChange):
 	def _parse_data(data):
 		"""Parses a sud.json document into the (name, description, schedule,
 		pot_mass, pot_material) tuple Sud needs. Computed up front rather
-		than assigned straight onto self, so a malformed upload() can't
+		than assigned straight onto self, so a malformed load() can't
 		leave a half-applied schedule in place."""
 		name = data.get('Name', '')
 		description = data.get('Description', '')
@@ -78,7 +78,7 @@ class Sud(AttributeChange):
 
 	def _reset_run_state(self):
 		"""Resets run-time progress back to a freshly-loaded, not-yet-started
-		IDLE state. Shared by __init__, upload(), and stop()."""
+		IDLE state. Shared by __init__, load(), and stop()."""
 		self.index = -1
 		self.hold_remaining = 0.0
 		self.state = SudState.IDLE
@@ -86,13 +86,13 @@ class Sud(AttributeChange):
 		self.user_message = None
 		self._paused_from = None
 
-	def download(self):
+	def save(self):
 		"""Returns the sud.json document currently on disk, for a client to
-		edit and hand back to upload()."""
+		edit and hand back to load()."""
 		with open(self.path) as f:
 			return json.load(f)
 
-	def upload(self, data):
+	def load(self, data):
 		"""Replaces the schedule with a new sud.json document and persists
 		it to disk, resetting to IDLE as if freshly loaded from that file.
 		Refused while a brew is in progress, or if data is malformed - in