Allow for exact match on the drug/chemical name

[newgene]

An example query for cisplatin returns 33 hits including matches like cisplatin complex etc.

https://mychem.info/v1/query?q=cisplatin&fields=_id&size=50&fields=chembl.pref_name,pharmgkb.name,aeolus.drug_name,%22unii.display%20name%22,umls

while this query is correct, we should create a way to return hits only match cisplatin exactly, like a keyword-indexed field called name.raw for this purpose.

[DylanWelzel]

Feature added with #179 and currently live, examples: https://mychem.info/v1/query?q=name.raw:%22cisplatin%22&size=50&fields=chembl.pref_name,pharmgkb.name,aeolus.drug_name,%22unii.display%20name%22,umls https://mychem.info/v1/query?q=name:%22cisplatin%22&size=50&fields=chembl.pref_name,pharmgkb.name,aeolus.drug_name,%22unii.display%20name%22,umls