Include # of failed builds in Subject
Let Builds.timestamp refer to the time the build was added

Previously, for scheduled builds, "timestamp" contained the time the
build was added to the queue, while for finished builds, it was the
time the build finished.  Now it's always the former.
Ensure that stoptime and starttime are set for finished builds
Remove unused Jobs columns

Actually, we can *almost* get rid of the Jobs table entirely...
Make latest/latest-for more efficient

Getting all matching rows from the database is expensive.