Don't need to kill db_stats.sh script

The sar and pidstat processes are handled differently now, such that we
don't need to try to kill the parent script.
Use dbgen to overwrite any existing files

Since it has a flag, then we don't need to have a separate line to do an
rm.
Update report script to plot database stats

This is using the scripts from the separate dbttools package.
Add option to collect 1 min of linux perf data

Arbitrarily set the length.  If it's too long, the perf tools will stall
on too much data.
Move all oprofile bash functions into main profile