Add MongoDatabase::importMoleculeFromIdentifer() method

This adds a new method to the MongoDatabase class which allows the
application to import new molecules from a molecular identifer (e.g.
InChI or SMILES).

Change-Id: I9cb2a2e3213474bcb31d82778b85a012615c09fc
Change CSV importer to create new molecules if not found

This updated the CSV importer to automatically import new molecules
from their identifiers if they are not found in the database.

Change-Id: Ia472e419243f4002cfba3797ee977f184560c76a
Merge topic 'import-molecule' into master

b0937fa0 Change CSV importer to create new molecules if not found
5c37e765 Add MongoDatabase::importMoleculeFromIdentifer() method