allow users to store a preferred start tab in a cookie

[alanb2718]

A feature request from one of our testers:

If you log in as an area, you almost certainly want to go to the Meetings tab. (Not true for regions or zones though.) So we could provide a way to optionally set the default tab to open when you log in, using a cookie, just as the preferred language is set with a cookie.

I like the cookie idea better than having the behavior for area logins be just flat to go to the Meetings tab.