introweb: fix connection hints for server announcements

A long time ago, the introducer's status web page would show the
advertised IP addresses for all published services, by parsing their
FURL's connection hints. This hasn't worked since about 12-Aug-2014 when
foolscap-0.6.5 changed the internal format of these hints (the column
has been empty this whole time).

This removes the "Advertised IPs" column from the Service Announcements
table. Instead, the service's full connection hints (not just the IP
address) is displayed in a tooltip/popup on the "Announced" timestamp
column.

The code that pulls these connection hints is now tolerant of all three
foolscap styles:

* foolscap<=0.6.4 : tuples of ("ipv4",host,port)
* 0.6.5 .. 0.8.0  : tuples of ("tcp",host,port)
* foolscap>=0.9.0 : strings

fixes ticket:2510