Windows support

These are a few changes to better support Windows.  We may want to add a warning to the documentation that we don't really want to support Windows, but are just including it as is.
I think it's worth mentioning the alternative solution, which is to switch from bcrypt password storage to sha512. In the file `girder/conf/girder.local.cfg`, change the following line from "bcrypt" to "sha512":

    [auth]
    # Use "bcrypt" or "sha512"
    hash_alg: "sha512"

Then they won't have to go through the hassle of installing bcrypt at all.