[writer] scan names with underscore instead of dot
https://github.com/silx-kit/silx/issues/3139
There is a suggestion to have the scan entrees in the Nexus file to be names 1_1, 1_2, 2_1, 3_1, ... (valid Nexus) instead of 1.1, 1.2, 2.1, 3.1, ... like in the spec file (invalid Nexus).
I there anyone relying on the dot notation? @sole @pithan @meyer @matias.guijarro @wright