Extend pull sheets to generic & cancer datasets

[ericblanc20]

Is your feature request related to a problem? Please describe.
Pulling sample sheets for generic &/or cancer datasets is currently not possible, because the code expects a family tree.

Describe the solution you'd like
pull_sheets.py can be trivially extended to cope with these situations

Additional context
In addition to the family-related extensions, it is also possible to use the library name as a default for the folder name in the IsaNodeVisitor class.