MATH-1008
Created package "o.a.c.m.fitting.leastsquares" to contain a modified version
of the contents of (to-be-deprecated) "o.a.c.m.optim.nonlinear.vector", the
main purpose being to provide a new "fluent" API (cf. "withXxx" methods).  
Along the way, class "LevenbergMarquardtOptimizer" has been further cleaned    
up (e.g. removing protected fields and deprecated methods and using local
variables instead of instance fields).
An additional constructor was necessary in "BaseOptimizer".


git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1508481 13f79535-47bb-0310-9956-ffa450edef68