SRA export only picks up first measurement type from i_.txt file

[djcomlab]

When doing a SRA export, the converter only picks up first measurement type from i_.txt file. For example in BII-S-3, there is metagenome sequencing and transcription profiling. This determines what is set in the study.xml file:

<STUDY>
   <DESCRIPTOR>
      <STUDY_TYPE existing_study_type="{value according to measurement type}"/>

In cases where there is only one assay type in the study, or one assay only, this shouldn't be a problem. But where multiple measurement types are used, the SRA export defaults to picking the first assay in the list. This could cause errors in the SRA depending on the content of the input ISA tab.

See also ISA-tools/isa-api#129