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
remove some empty CSS clutter
make FsFile constructor more permissive
use Deque in CheckedPath
use Deque in FleetingDirectory
add curly braces
remove whitespace
update copyright headers
Merge pull request #2723 from mtbc/minor-deque-tidyup

minor Deque tidy-up (rebased from dev_5_0)
Merge pull request #2715 from joshmoore/rebased/develop/ipv6-error

Don't swallow error on startup (rebased onto develop)
Merge pull request #2717 from mtbc/empty-css

remove some empty CSS clutter