Safer linking, windows support (?)

No file is move until a link is made in the same directory. No file is deleted until the link is actually in place. This is a much safer way of doing things.

I think windows is a go, I'll test it presently.
handling no Installed Packages, overwriting links

If Installed Packages is empty, and the settings storage is a git repo, it won't exist. On linking, make an empty folder first.

Symbolic links can now be overwriten by symbolize (previously, rmtree would be attempted instead of os.remove