change results of text.nameext_from_url()

Instead of getting a complete 'filename' from an URL and splitting that
into 'name' and 'extension', the new approach gets rid of the complete
version and renames 'name' to 'filename'. (Using anything other than
{extension} for a filename extension doesn't really work anyway)

Example: "https://example.org/path/filename.ext"

before:
- filename : filename.ext
- name     : filename
- extension: ext

now:
- filename : filename
- extension: ext

test/test_downloader.py

@@ -45,7 +45,7 @@ class TestDownloaderBase(unittest.TestCase):
         kwdict = {
             "category": "test",
             "subcategory": "test",
-            "name": name,
+            "filename": name,
             "extension": extension,
         }
         pathfmt = PathFormat(cls.extractor)