Store measurements in a local database to reduce plotting time
We want to add graphs to OnionPerf that compare larger numbers of measurements. We also plan to add more parameters to plot different subsets of measurements. Having a local database for storing measurements and decoupling the parsing step from the plotting step might reduce overall plotting time. This will be particularly useful when we include graphs based on Tor descriptors like flags or bandwidth or consensus weight.
Part of this ticket will be to figure out which database to use. Maybe we need to experiment with SQLite to see if it's fast enough for this purpose or whether we need something like PostgreSQL here.