Add row/column names to outputs when row/column names are provided in inputs

[pcarbo]

An example:

> head(X)
           x1      x2      x3      x4      x5
[1,]  0.03304  0.1140  0.3275  0.5706  0.3369
[2,] -0.01010  0.1207  0.5777  0.5615  0.1652
[3,]  0.81061  0.6984 -0.6451 -0.8045  0.3952
[4,]  0.67726  0.6801  1.2551  1.2428  1.0316
[5,]  0.71058  0.6969 -0.3221 -0.5285  0.3305
[6,] -0.50743 -0.5174 -1.1044 -1.0052 -0.5325
> head(fit$alpha)
            x1        x2       x3      x4      x5
[1,] 0.0005016 0.0005132 0.629070 0.31765 0.05227
[2,] 0.4661892 0.4776898 0.009709 0.01153 0.03488

This is a common feature for linear regression methods in R.

[gaow]

Added to cran todo list #111