Generate quality report for each data source

[grishagin]

For each datasource:

find where multiple records from a single source point to the same stitch node -> for example, the (R) and (S) versions of a substance are mapped to the same stitch node

structure incorrect? -> record winds up in a stitch node not linked to by stuct (L4 lychi) --- Broad Doxorubicin is a good example of this

think up other self-consistency checks as well ...