Add upload save feature

Add /api/upload-save endpoint that streams the data via the slave
assigned to the target instance to the instance saves directory, along
with a ctl command and web interface button to do the upload.

packages/web_ui/src/index.css

@@ -164,6 +164,10 @@ body {
 	white-space: pre-wrap;
 }
 
+.save-list-dragger .ant-upload.ant-upload-btn {
+	padding: 0;
+}
+
 .rcon-result code {
 	display: block;
 	background: #000;