Document and alter the pconn idle timeout directives.

Document and alter the pconn idle timeout directives.

Alters the directive names to clarify what they do and adds some more
description to the config file documentation.

Alters the internal config variables to match the new directive names.

Also alters the well known messages in mgr:filedescriptors report a little
to indicate client/server type and adds a standard "Idle " prefix for
easy automated scanning.