error codes used by subroutine task_error:

normal or info messages:       1xx, 2xx
warnings:      		       3xx, 4xx
minor errors:		       5xx, 6xx
errors:			       7xx, 8xx

The faimond-gui has 4 icons for the error levels.

The variable $STOP_ON_ERROR (default 700) will define that return
codes that are greater the this value will stop the installation.
