battery.m: repeatedly call bfgs using a battery of 
 start values, to attempt to find global min
 of a nonconvex function

 INPUTS:
 func: function to mimimize
 args: args of function
 minarg: argument to minimize w.r.t. (usually = 1)
 startvals: kxp matrix of values to try for sure (don't include all zeros, that's automatic)
 max iters per start value
 number of additional random start values to try

 OUTPUT: theta - the best value found - NOT iterated to convergence

Package: optim