Add unsigned arrays to array template

[JakeWharton]

These are still experimental and so an annotation propagating that is added to the codegen for these types only.

I've modified the TemplateTask to support multiline declarations. I did it in a separate commit since it's technically orthogonal to the unsigned change.

[JakeWharton]

Good to merge?

[evant]

😕

[JakeWharton]

Ah it only tells me this:

I'll get it ready for a rebase instead tonight.

[JakeWharton]

Better?