add scaffolding support to pub

[DartBot]

<img src="https://avatars.githubusercontent.com/u/84659?v=3" align="left" width="96" height="96"hspace="10"> Issue by polux
Originally opened as dart-lang/sdk#7181

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It would be nice for those not using the editor if pub had some command along the lines of

  pub init <project_type> <project_name>

that would create a pubspec.yaml file, lib/bin/web/test/... directories and maybe a lib in lib or a page and a lib in main. It could also ask for the project author's name, the license (and have a built-in set of licenses), etc.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/5479?v=3" align="left" width="48" height="48"hspace="10"> Comment by sethladd

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This would be cool!

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Added Triaged label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/46275?v=3" align="left" width="48" height="48"hspace="10"> Comment by munificent

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Added Duplicate label.
Marked as being merged into #34.