System wide Pkg installation

@johnh I am using environment modules to manage loading Julia itself (and other binary dependencies), but I haven’t found any way of making it interact with the Julia package manager. What I would really like is if JULIA_PKGDIR became JULIA_PKGPATH, allowing multiple directories to be searched in a defined order. It would also be good if there was some environmental variable that corresponds to LOAD_PATH, but I don’t know of one.

@ianabc Could you have a login script symlink everything in the system package directory into the users package directory?