queue launcher does not create an .err file if an error occurs

[duylethanh]

As the title says, the queue launcher does not create an .errfile, if an error occurs in simexpal.
For example: Using @INSTANCE@ in experiments with fileless instances causes RuntimeError: The instance 'foo' is fileless(assuming the fileless instance is called foo)

We should redirect such errors to an .err file in the aux/_queue/ directory just as simexpal does it for experiments launched with Slurm.

(Implement this while fixing #108)