German translation fix (JabRef#1988)

* Generalize german translation of database into "Datenbank"

* add changes to CHANGELOG.md

* Some spelling fixes

* Fix some spellings, change confusing translations

* revert changes of "importieren", change translation of shared database, add that information to the CHANGELOG.md

* Fix typo

* Replace database translated as Datei with Datenbank, streamline importieren

* Remove unused keys

* Revert changes, improve translation

* add missing German translations, use Umlaut directly in Menu_de

* Add missing underscores

* Remove unrelated CHANGELOG entry

* Remove duplicates

* Add missing German translations

* Fix typo

Author: mairdl

CHANGELOG.md

@@ -54,6 +54,8 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - [#490](https://github.com/JabRef/jabref/issues/490) Added right click menu to main table and entry editor to allow copying doi url
 - [#549](https://github.com/JabRef/jabref/issues/549) Added new shortcut to copy the BibTeX key as a hyperlink to its url to the clipboard
 - Complete vietnam language translation in menu
+- Generalize German translation of database into "Datenbank"
+- Improve language quality of the German translation of shared database
 
 ### Fixed
 - Fixed [koppor#160](https://github.com/koppor/jabref/issues/160): Tooltips now working in the main table
@@ -82,6 +84,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - Fixed [#1958](https://github.com/JabRef/jabref/issues/1958): Verbatim fields are no longer checked for HTML encoded characters by integrity checks
 - Fixed [#1937](https://github.com/JabRef/jabref/issues/1937): If no help page for the current chosen language exists, the english help page will be shown
 - Fixed [#2060](https://github.com/JabRef/jabref/issues/2060): Medline fetcher now imports data in UTF-8 encoding
+- Fixed file menu displays wrong hotkey in the German translation
 
 ### Removed
 - Removed 2nd preview style