Fix coding error.
Use internal multi-start BOBYQA optimizer rather than Commons Math MultiStartMultivariateOptimizer.
This allows us to use a different initial trust region radius, chosen for the specific start point,
for each start.  We need this because BOBYQA will alter the start point if the radius is too big.
It also gives feedback with each start.
Promote Multi-Start optimizer to a separate optimizer type.  If the caller doesn't supply a range processor,
use RandomRangeProcessor with 30 starts.
Drop Powell from the list of optimizer types the user can select in OptimizationPreferences:
it is too dangerous because it doesn't respect the bounds.
Merge remote-tracking branch 'origin/master'