Changes header links on index

- Now only shows the signup button if not logged in
- Replaces signup with link to own ladder if logged in
Adds deleting matches from the standard interface.

UX is horrible -- blocks until the entire company has been updated.
Adds auto-refresh functionality.

Companies now save their last changed time. Viewing a player or the
ladder will automatically reload the page if the underlying company is
re-saved. Currently polling happens every 60 seconds.