Add a cookie to persist user settings

[NickMOrlando]

Whenever I buy a new expansion, I only print the tabs I need for the new expansion.

Unfortunately, I almost never remember all the options I picked for the tabs I already have printed.

When I visit the bg_tools website, it would be nice if my previous selected options were persisted (possibly within a cookie) so that I don't have to remember all the details of the options I selected the last time.

[sumpfork]

Also see sumpfork/dominiontabs#123 - we already have some basic functionality to save options, would need a way to load them in the web interface.