Reduce Ice-generated C++ warnings

Rather than simply listing (and ignoring) all the warnings
that come with ZeroC-generated code we now suppress their
output at the cmake level.

In addition, using `cmake -Dfatal-warnings=true .`
will make all warnings an error which forces cleaning
up these issues.
Surround more Ice-generated includes
Also handle unused arguments
Also handle missing declarations
Also fix overloaded-virtual
Suggestions from Roger incl. strict push/pop

The `#error` on re-entrant warning protection
showed a number of places where the includes
needed to be adjusted.
Fix tests warnings
Fix casts in combined.vm
cmake: Add feature tests for warnings
Use vector.clear() rather than static_cast

Suggested by Roger that `static_cast<>(0)` for vectors
is confusing and possibly wrong.
Temporary modifications of fatal-warnings flag

In order to have fatal-warnings propagated to examples
and tests, it needs to come before the add_subdirectory
calls. Also, since we still have deprecated code, it's
necessary to ignore those globally in order to have the
build succeed.
Handle broken image links in public shares correctly as before #3124
adding deleted objects to the subtree
Merge pull request #4 from aleksandra-tarkowska/public_broken_links

Instead of default 'Image' indicate that images are deleted in the tree
Fix admin_only decorator in omero.cli
Fix CLI plugins to use admin_only across the board
Add integration tests to cover admin_only checks
Pass omero.db.pass via envvar to bin/omero admin reindex

For security reasons, the DB password is not passed as an xargs to the reindex
command. This commit fixes this issue by internally setting the JAVA_OPTS
environment variable which should only be visible to the process owner (and
root).
Remove fatal-warnings flag in favor of BF version
More static_cast fixes after extra-warnings

Turning on extra-warnings shows a number of errors
that were not previously fixed. This commit fixes
a few whitespace issues and surrounds casts from
size_type to Ice::Int with `static_cast` to remove
the conversion warnings.