take into account MRREL concepts in different datasources

[fpriyatna]

This addresses issue #41

[fpriyatna]

This patch only works for load-by-cui

[fpriyatna]

wc -l MED-RT_codes-original.ttl
43204 MED-RT_codes-original.ttl

wc -l MED-RT_codes-patched.ttl
43204 MED-RT_codes-patched.ttl

wc -l MED-RT_cuis-original.ttl
112339 MED-RT_cuis-original.ttl

wc -l MED-RT_cuis-patched.ttl
311549 MED-RT_cuis-patched.ttl

So we can see that with this patch applied we get 199210 more lines/triples (311549 - 112339).

Notice how loading on codes has no difference.

[jonquet]

I would wait for #41 to converge before merging this.