Improve handling of network errors

[dominikl]

Sometimes Insight crashes on network/connection issues, when it actually should be able to recover from them. When it's not possible to recover there should be at least a better error message for the user.

See for example 28982

[dominikl]

Another example: https://www.openmicroscopy.org/qa2/qa/feedback/29290/ .
Unfortunately one can't replicate the problem by simply disconnecting and reconnecting the network. I have to try with a VM and netem at some point.

[dominikl]

Adding more bug report here:

• 29450
• 29574

[dominikl]

The reason why reconnecting sometimes work and sometimes doesn't is how the data from the server is requested. If it is through the OMEROGateway then it's fine, because exceptions are handled by

omero-insight/src/main/java/org/openmicroscopy/shoola/env/data/OMEROGateway.java

Line 783 in 3631862

boolean handleConnectionException(Throwable e)

(which opens the connection issue dialog and tries to reconnect), whereas if the Java Gateway is used directly, then the exception isn't handled and Insight crashes. So probably all uses of the Java Gateway have to reviewed and wrapped into respective methods in the OMEROGateway which catches the Exceptions.

[dominikl]

These cases have been dealt with. But it looks like there are more, created a new issue for them: #430