add some scale transforms?

[shabbychef]

I have a 'quiver' of scale transforms I keep at my disposal, and was looking to put them in a package. It makes no sense to have a package just for them, but maybe ggalt would be a good place. For example, 'signed square root':

scl_ssqrt <- scales::trans_new("signed sqrt",
  function(x) sign(x)*sqrt(abs(x)),
  function(y) sign(y)*y^2)

Similarly I have scales for asinh, logit, inverse logit, and so on. Just one-liners! Certainly not worth their own package, but maybe they belong in a 'grab bag' package.