Database changed to improve website performance

Added columns to the results database to keep track of the on time rate
for the arrivals instead of calculating it every time a page on the
website was loaded, and added a method to MuniLine to calculate the
on-time rate. Also added columns to the results table for the number of
scheduled arrivals at a stop and the actual number, and created a table
to keep track of missed runs, both of which are features that will be
implemented shortly.