Refactor plugin code base

- The rateLimit class stores timeLapse as an integer.
  PeriodicRateLimiter stores timeLapse as Long, which confuses
  understanding and using the code. This change converts all timeLapse
  variables to an integer.
  
- Remove timeLapse from warning rate limiters, since timeLapse can be
  accesed from delegate
  
- Add methods getWarnLimit and getTimelapse

Change-Id: I0bb96c3c2309ee911a667d138992613d3cf36d67