Allow to restore dll from remote dependencies file #1507

From https://gist.github.com/forki/be1fe52828dc4a9f3729#file-gistfile1-txt-L6

Let's try a concrete example. privateeye.fsx has a dependency on privateeye.bridge.dll. What I would like to do is in my repository put up a paket.dependencies that specifies when you want privateeye.fsx /bin/privateeye.bridge.dll should also be downloaded.

The following is intended to work:

• https://github.com/PrivateEye/PrivateEye will contain
  • privateeye.fsx
  • /bin/privateeye.bridge.dll
  • paket.dependencies (with reference to /bin/privateeye.bridge.dll)

User repo has a paket.depndencies file like this:

source https://nuget.org/api/v2
nuget bla
github PrivateEye/PrivateEye privateeye.fsx

Running paket restore should download privateeye.fsx and /bin/privateeye.bridge.dll

/cc @gregoryyoung