index score column and faster row counting

[bwhall61]

Added indexing to the scores in the SQLAlchemy database for faster ordering
Commented out some variables that were unused
Implemented a faster way to count the number of molecules in the database (just for showing the number of pages in the UI I think)

[bwhall61]

I can add another commit later - but I realized some other columns in the sqlalchemy db maybe should be indexed.

Molecule:
run_id

Grade:
mol_id
hp_settings_id
timestamp

These are all used to exclude and filter molecules in get_ordered_molecules and indexing them makes submitting scores and switching between pages much faster. I don't think the impact of having many indices in the db will matter too much for us?