cargo: list packages matching name

[graydon]

"cargo list foo" or "cargo search foo" should return a list of packages matching foo, including installation-status and (if installed locally) where they're located in the search path, and possibly the short package desc / license / version.

[elly]

https://github.com/graydon/rust/pull/1363 handles this.

[catamorphism]

I'm closing this since #1363 appears to have been merged.