Moved performance test tuning into JUBProvider

Logic to estimate JUB test method benchmark rounds required to run for
a total of 5 seconds, save those multipliers to a file, read them, and
modify the JUnitBenchmarks configuration accordingly is now
concentrated solely in JUnitBenchmarkProvider, instead of being split
across JUnitBenchmarkProvider and GroovyTestSupport.  The
implementation uses java.lang.reflect.Proxy to generate a dynamic
proxy annotation instance and intercept JUB's call to the
benchmarkRounds() method for each test.  This is sort of byzantine,
but it's the best I can do, given the severe limits on inheritance in
both JUnit and JUnitBenchmarks via the final keyword and restrictive
method visibility modifiers.
Comment changes, cleanup in JUnitBenchmarkProvider
Trying five BB.duplicate() removals w/ Cassandra