Keep errors out of the display/history

[Former user]

Originally reported on Google Code with ID 167

They are useless information, so a dialog should be shown instead, telling
the error to the user without adding the message to the display or history.
Special attention must be payed while implementing the feature in the case
of session importing.

Reported by helder.pereira.correia on 2008-03-14 23:21:23

[Former user]

``` Implemented in trunk (revision 1138). In the particular case of session importing, a dialog shows up asking whether the error shall be ignored, all the errors shall be ignored or to cancel. ```

Reported by `helder.pereira.correia` on 2008-03-14 23:24:28 - Status changed: `Fixed`