Add id as an AutoNumber(primary_key=True) field and remove the pk from

Add id as an AutoNumber(primary_key=True) field and remove the pk from
library_id.

Stanford decided to use library_id as a text field so they could use
library IDs like "SL100". Caltech just used the raw sql id, so the
foreign key reference in experiments_flowcells was expecting a numeric
id, but since the model had the text field as the primary key things
didn't work.