Corrected ChEMBL license
Version-level shape expression for the Core properties
Added versioning properties to version-level
Combined shape description into single file to enforce version description linking to entry description
Added provenance links to source datasets.

Note that the validator does not validate the linked resource since it is of the same shape expression and therefore worried about entering a cycle.
Added frequency of change to be a resource
Frequency limited to terms coming from the DC Frequency vocabulary
Language declarations must come from lexvo namespace
Previous version must point to a Version-Level description