Werk #11720: Cleanup graphs and check output for network interface checks

All graphs showing average metrics (e.g. "In_avg15" for the 15-minutes average value of incoming traffic) have been removed from all interface services, as the underlying value is only needed for evaluation of average-based warn/crit levels and the graph adds no additional information to the normal output.

All displayed graphs now show the absolute value of the corresponding rate, independent of the type of the specified warn/crit levels (percentual, absolute). This had not been the case for errors, multicast and broadcast graphs.

All available packet rates, i.e. unicast, non-unicast, multicast, broadcast, errors, discards, are now displayed in the detailed service output. The values will be shown as percetual or absolute values, depending on the type of the underlying warn/crit levels, with the absolute value being the default, if no levels are specified. Please note that for error levels, there is a default of warn:0.01% and crit:0.1%, therefore, the error rates will be displayed in percent by default. If averaging is activated for the packet rate levels, the corresponding average value will be displayed instead.

Finally, the bandwidth graph has been moved up to the top of the displayed graphs.

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