non numeric values in drug_descriptor table that should be numeric

[ymahlich]

Some drug descriptor_value fields for certain structural_descriptors contain non-numeric faulty data where there probably should be a numeric value.
We should remove those entries during the build process, since some other structural_descriptors like morgan_fingerprint are inherently non-numeric and pose problems if the casting to numeric is done over the full drug_descriptor table.

Specific example:

Dataset: MPNST
structural_descriptor: AATS0s
improve_drug_id: SMI_1550
descriptor_value: 'missing intrinsic state for [...]'