Upstream has officially abandoned the project as of 2021 [0], there's been
no release since 2016, it uses the EoL Qt 4, and alternatives like
KeePassXC exist.
Also move KeePassXC to its own directory -- it doesn't make sense to
have it in KeePassX's folder anymore.
[0]: https://www.keepassx.org/index.html%3Fp=636.html
