A bug has been found in the processing of the variance: we were using a naive formula that is ill-fitted to signals showing small variations around a large mean. This lead to catastrophic cancellation and negative values... This has been replaced by a (slower) compensated formula (that works in two passes). The standard deviation filter has been fixed. 

The Tukey filter has been brought back into the new infrastructure and should now be usable. However it is not suitable to snow heights: in such a case, the standard deviation is too small (or even zero) and the signal might show some sudden variations (like in the case of a snow fall) that would therefore be falsely rejected. This filter seems much better suited to wind speeds that exhibit some constant background noise, thus a non-null standard deviation.

The rate filter can now take 2 arguments: in such a case, the first one is the minimum rate and the second the maximum rate. This would allow to define a descent rate different from the climb rate.

Several error messages have been improved in A3DIO and general plugin loading.

Finally, two small tools for working with smet files have been contributed, one allowing transparent loading of smet files in xmgrace (smet2agr). And the example io.ini has been fixed (it had been broken and was not working with the examples anymore)