Allow scaling of init functions

[mcabbott]

This allows init = 2 * randn32 to scale the initial values.

Implemented as a struct like Fix1, in order that 2 * randn32(rng) can also work.

Should probably apply to every function, and needs tests etc. But is this a good idea, first?

PR Checklist

• Tests are added
• Entry in NEWS.md
• Documentation, if applicable

[ToucheSir]

My inclination is that init = (args...) -> 2randn32(args...) or init = (args...) -> lmul!(2, randn32(args...)) isn't significantly more boilerplate and is a little more flexible in terms of supported operations. Perhaps documenting this pattern would be the way to go?

[darsnack]

I feel the same way. A neat trick but seems like too much for something that is easily implemented as an anonymous or one line function.

[mcabbott]

Ok, I think I agree this is too much. Better to stay closer to Base... and if in doubt you should make the matrix yourself.