Adds brute force and multiple starting values to nls.
o algoirthm can be "plinear-brute" or "plinear-random"
o corrected one nls2 example
o trace is now used by nls2 to control printing. Previously it was only used to pass to nls.
o corce formula argument to a formula if its not already a formula
o NAMESPACE file added
o as.lm removed
o as.lm and as.lm.nls can be used to convert an "nls" object to an "lm" object which is tangent to the nls object. Untested.
o as.lm.nls uses proto package hence new dependency
o added algorithm = "random" which samples maxiter rows from start if start is a data frame with more than 2 rows whereas if start is a data frame with exactly 2 rows it will take maxiter random points from the rectangle whose boundary is defined by the rows.
o if nls exits with an error nls2 uses NA as the return value of that nls call instead of stopping with an error
o fixed problem with update not working with objects produced by nls2.
o fixed number of iterations and tolerance displayed when using algorithm = "brute-force".
o if there are exactly two rows in start= then a grid of starting values is formed so that there are at least maxiter points on the grid.
o start can be an nls object in which case coef(nls) is used.
o documentation and DESCRIPTION file tweaks.
o initial release.