Ice default encoding (rebased onto develop)



This is the same as gh-1602 but rebased onto develop.

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In order to permit Ice 3.5 clients to work with Ice 3.3 & 3.4 servers, set the `Ice.Default.EncodingVersion` to 1.0 for all OMERO4 SDKs. To the implementation:

 * `Ice.Default.EncodingVersion` should not be set for Ice 3.3 & 3.4 since warning "unknown property" will be printed.
 * The value can be forced to `1.0` via `$ICE_CONFIG` or similar.
 * A fallback mechanism should be used instead on OMERO5 if possible, but the change was too invasive for 4.4.9.

CC @rleigh-dundee @jburel @pwalczysko

In order to test, find an Ice 3.5-based client (Java, Python, C++) and try to connect to a non-Ice 3.5 server without this PR. You should get a `Ice::UnknownLocalException( --> Ice::UnsupportedEncodingException)` message. With this PR, it should work. If you specify `Ice.Default.EncodingVersion=1.1` in `ICE_CONFIG` you should see the failure again.