Add line number from source data file to import script and database

[epoz]

Add a facility to the make_import.py script to record the line number in the notations.txt file being used, and record that in the resulting iconclass.sqlite file.
The database schema should also be updated to accommodate this, plus the commit hash of the repo being used.

These line numbers and the data repo commit hash can then be used to create links in a UI to display an exact reference to the end-user to invite them to view the sources.