add Material.Builder(URL fileURL)

[kazurayam]

not only URL in http:// + https://, but also file:

[kazurayam]

I made a test as follows:

    @Test
    public void testFileURLSupport() throws MalformedURLException {
        String fileUrlString = "file:/Users/who/bar/baz.txt";
        URL url = new URL(fileUrlString);
        Metadata md = new Metadata.Builder(url).build();
        System.out.println(md.toJson(true));
        assertTrue(md.containsKey("URL.protocol"), "URL.protocol is not contained");
        assertEquals("file", md.get("URL.protocol"));
        assertTrue(md.containsKey("URL.path"), "URL.path is not contained");
        assertEquals("/Users/who/bar/baz.txt", md.get("URL.path"));
    }

It emitted :

{
  "URL.host": {
    "key": "URL.host",
    "value": ""
  },
  "URL.path": {
    "key": "URL.path",
    "value": "/Users/who/bar/baz.txt"
  },
  "URL.protocol": {
    "key": "URL.protocol",
    "value": "file"
  }
}

So the file URL is already supported by Metadata.Builder(URL) method