add additional biosample identifiers as columns

[realmarcin]

this depends on what's available in the XML file. any of EBI, INSDC, SRA sample ids would be useful for allowing to link to other data.

along those lines, sometimes samples have children and parents, so adding the parent sample ids would allow to group/stratify the biosample table rows more precisely.

[realmarcin]

@wdduncan do you have any thoughts on this? this likely involves going back to the xml and deriving new columns?