As discussed in #4317, the next KeePass2 release will ship with
support for a new generation of XML key files which enable
hash integrity checks.
This patch adds support for reading and generating this new format.
By default, KeePass2 now uses the .keyx extension for generated
key files, which was added to KeePassXC's key generation file chooser
filter. We continue to generate hashed binary key files by default,
but the user can explicitly save the file with the new .keyx
extension to generate an XML v2 key file (currently undocumented).
When opening a database, the key file type is still determined
by content negotation, so the file extension has no impact here.
As an additional change, the legacy key file warnings have been
improved slightly to be less confusing and more helpful.
Definitions:
* Database Key - Cryptographic hash used to perform encrypt/decrypt of the database.
* Database Credentials - User facing term to refer to the collection of Password, Key File, and/or Hardware Key used to derive the Database Key.
Changes:
* Remove the term "master" and "key" from the user's lexicon and clarify the code base based on the definitions above.
* Clean up wording in the UI to be clearer to the end user.
