add a sensor for reqs-per-sec for mysql, since it was easy (we were running the command anyway);
and some string mangling routines to help simplify, in case we want to do more such
add a CountdownTimer to simplify writing code to check for expiry, building on duration

for instance get an `Duration.FIVE_SECONDS.countdownTimer()`, wait 5s, then invoke `isExpired()` will return true
cleans up restart logic, so it is smart about whether it needs to do an entity.start() or a driver.launch(), and related fixes which caused problems including setting sensors and creation/recreation of sensor feeds
code review - doubles supported for duration, and tabs fixed in that bit of SoftwareProcessImpl
Merge pull request #942 from ahgittin/feature/mysql-etc

improvements to restart logic, esp for nginx; and related