FIX BlockMeta repeat #20 ?

[atravert]

In some instances, multiple entries with same name - in particular 'AB' seem to be present. In case of 'AB' only the the first one is valid. The supplementary instances are kept and added in the dict with a key ending by '(1)', '(2)', etc...

This should fix issues #20 and #15

[philipp-baumann]

Can confirm this. So far I have only found files with two spectral AB or Refl blocks, because of atmospheric compensation. That is how we deal in the R implementation. To join knowledge, would be great to know if this "additional_type" can be only 0 or 64, or actually have more representations (what you have solved with the dict stated above). https://github.com/spectral-cockpit/opusreader2/blob/e503ce3ae51155a77a1f94bae8eff9af1092fae4/R/read_header.R#L33