Don't swallow error on startup

Startup errors which could point to the actual failure
were being swallowed by Blitz. NB: This particular error
condition was initially related to the Ice.IPv6 setting.

See:
* https://www.openmicroscopy.org/community/viewtopic.php?f=5&t=7527
* https://www.openmicroscopy.org/community/viewtopic.php?f=5&t=7456&p=14166#p14166
Introduce an optional IPv6=0 property

While we're at it, might as well place
an anchor in templates.xml so users can
more quickly find the formatting needed
to disable IPv6.
Improve templates.xml explanation
Merge pull request #2689 from joshmoore/ipv6-error

Don't swallow error on startup