RFC: Record copied artifacts in build action

Which artifacts are copied in a certain build is as important as knowing the exact SCM revisions it is based on. So it should be displayed as prominently.

* Show list of source projects and builds on build page
* Add new sidepanel entry with detail page listing copied files

Screenshots below.

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This is a request for comments on this implementation and shouldn't be merged yet. Is this complete? I'm not using matrix or Maven projects, so I'm really interested in information on those.

(Work in progress: weird difference needed to cover both flattened and unflattened copying; unknown whether `Run.XSTREAM2` is the right place to define aliases; insane approach to getting the current build's `sidepanel.jelly`; no full localizability; no tests; not making sure anchor names are valid)

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![screen shot 2014-02-20 at 01 07 20](https://f.cloud.github.com/assets/1831569/2213635/27a7a440-99c3-11e3-9fbd-bdd566145c15.png)

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![screen shot 2014-02-20 at 01 08 01](https://f.cloud.github.com/assets/1831569/2213636/27a7c77c-99c3-11e3-9f5b-f8bb3c609602.png)