New session management code is live on aprs.fi

[Heikki Hannikainen]

Hi,

Due to the increase in load placed on aprs.fi by various bots and data
collectors I had to rework the user session management code a bit, so that
I don't need to store as much session data on the backend service for all
those bots. Unfortunately it's still a common sport to try to use the
aprs.fi web *user* interface as an API, instead of connecting directly to
APRS-IS to collect the data directly from the source.

For new sessions there's also a proof-of-work javascript task which runs
on the clients, to make it more expensive for the bots to create new
sessions. This shows up as an additional "verifying your browser" view
when entering the station. I'm sorry for this nuisance.

There's a non-zero risk that these break something for real users. If you
find something broken, just reply here and let us know. Thanks!

- Hessu