GitLab

Previously the start time was read from the GPS measurement stored in
the metadata, but this differed from the filename. The filename is now
being used instead as it seems to be what is considered proper.
Solve issue with __sampleend method. It has the last real sample to
process, not with the "range" semantic (last not considered).

Even calling decimation with parameter 1 gave some small differences in
amplitude.
Limit the values that the decimation parameter can receive.

Use of wrong headers resulted in saturation of values.
Also add the metadata optional parameter.

Longer data blocks were giving a segfault.
Bug when end time window was undefined (None). Comparison failing.