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

gallery_dl/text.py

@@ -73,8 +73,8 @@ def nameext_from_url(url, data=None):
     """Extract the last part of an URL and fill 'data' accordingly"""
     if data is None:
         data = {}
-    data["filename"] = unquote(filename_from_url(url))
-    data["name"], ext = os.path.splitext(data["filename"])
+    name = unquote(filename_from_url(url))
+    data["filename"], ext = os.path.splitext(name)
     data["extension"] = ext[1:].lower()
     return data