Clean up / improve tag name aliases

[lbo]

as stated in https://www.photools.com/community/index.php?topic=9082.msg63847#msg63847, some of the alias names defined in immbcfg.xml should be improved to avoid misunderstandings.

Generally, I recommend to stick with the wording from ExifTool as far as possible as we already have too many wordings for the same data.

Specific entries I found worth mentioning:

4100 "Date Subject Created" -> "subject" is misleading and should be removed.

4100 "Thema erstellt am" -> "Erstellungsdatum" (ExifTool) or "Aufnahmedatum" (what it really means).

1800 "Created Date" -> "Create Date" and "Digitalisierungsdatum" (from ExifTool)

1900 "Original Date/Time" is mapped to the same tag as 4100, so we can't even select it in the tag selector. What is it good for?

1300 Belichtungsquelle -> Lichtquelle

Oliver