automatic edge between http:file and file

[purpleidea]

Automatic edges add dependencies between different resources.

For example:

$f2 = "/tmp/some_file"
file $f2 {
        content => "i'm a cool file in /tmp\n",
        state => $const.res.file.state.exists,
}

http:server ":8080" {
}

http:file "/file2" {
        path => $f2,

        Depend => File[$f2],    # TODO: add autoedges
}

We have an API to add these automatically. Add this feature for these two resources! Keep in mind that path can be a dir as well.
The examples/lang/http*.mcl examples should make this all easier to test.