Access to Memory (AtoM)

The CSV import CLI task is currently disregarding the --index flag when creating notes, events and relations. It is also using a Propel ORM query to check if a note already exists. Both of these issues are causing performance issues particularly when there are a large number of notes contained in a CSV row.

The performance of CSV import can be increased by making the following changes:
- ensure the creation of notes, events and relations respect the --index option.
- replace the notes table Propel query with a PDO query.