Improve the server options

[oeway]

Here are some suggested improvements for the server options:

• Move the server out from the advanced setting maybe.
• It would be nice if the app can use localstorage to store the selected server, so it won't forget next time.
• In the meantime, could you also add a local server option, e.g. http://127.0.0.1:9520, ideally detect whether it exists before adding the option. This will be useful if the user started the BioEngine server locally.