Snomed drug ext

[antsh3k]

SNOMED Uk drug extension format has been changed by NHS digital. Added a minor fix to resolve this. only changes to the medcat.utils.preprocess_snomed.py file were made.

[antsh3k]

This last commit is a bug fix. d1.update(d2) was replaced with d1 = {key: d1.get(key, []) + d2.get(key, []) for key in set(list(d1.keys()) + list(d2.keys()))}

[tomolopolis]

is this PR good to go?