If the value that has to be mapped is "None" the tool will keep the "None" value
Merge branch 'hotfix_570'
closes #570
galaxy wrapper can switch between the two sequencing data samples
import workflows (the one with the data objects and the one without
them)
Merge branch 'bug_569'
write 'None' in unput dataset when importing seq data samples if a
null sample_label has been provided