Use more consistent signature for methods of as.hyperSpec()

[GegznaV]

Currently, each method of as.hyperSpec() uses its own order, default values and number of arguments:

.as.hyperSpec.matrix <- function(X, wl = guess.wavelength(colnames(X)), ...)

.as.hyperSpec.data.frame <- function(X, spc = NULL, wl = guess.wavelength(spc), labels = attr(X, "labels"), ...)

.as.hyperSpec.hyperSpec <- function(X)

This makes it more difficult to use in other functions as each case should be addressed separately.
My suggestions would be to:

• use NULL for the default values in the signature and perform calculations or real initial values inside the methods;
• use consistent order of arguments;
• rename argument wl into the name that will be suggested in consistent naming of wavelength parameters #90.

May also be related: #144 (comment)

[cbeleites]

This is a very good point. +1

[GegznaV]

Moved and reopened as:

• Use more consistent signature for methods of as.hyperSpec() r-hyperspec/hyperSpec#16