Groups of links per analysis, other improvements.

It seems that submissions must be done in directories named after the
NCBI account of the submitter.
Meta data spreadsheet seem to be able to accomodate one type of library,
so one such directory is made per library type, with links to all data
of this type.
The workflow should fail if there are name conflicts due to repeated
file names once analysis directory is not present the path.

Files containg info about raw data in tab-separated format are created.
The content can be copy-pasted in the "RAW FILES" section of the
submission spreadsheet.