Add sharing of groups between databases

* Add source folder keeshare for sharing with corresponding define WITH_XC_KEESHARE
* Move common crypto parts to src/crypto/ssh
* Extended OpenSSHKey
* Move filewatching to own file (currently in two related classes DelayedFileWatcher and BulkFileWatcher)
* Small improvements for style and code in several classes
* Sharing is secured using RSA-Keys which are generated on demand
* Publisher signs the container using their private key
* Client can verify the signed container and choose to decline an import,
import only once or trust the publisher and automatically import all
data of this source henceforth
* Integration of settings into Group-Settings, Database-Settings and Application-Settings
* Introduced dependency QuaZip as dependency to allow combined export of
key container and the (custom format) certificate

README.md

@@ -35,6 +35,7 @@ so please check out your distribution's package list to see if KeePassXC is avai
 [Google Chrome or Chromium](https://chrome.google.com/webstore/detail/keepasshttp-connector/dafgdjggglmmknipkhngniifhplpcldb), and
 [passafari](https://github.com/mmichaa/passafari.safariextension/) in Safari. [[See note about KeePassHTTP]](#note-about-keepasshttp)
 - Browser integration with KeePassXC-Browser using [native messaging](https://developer.chrome.com/extensions/nativeMessaging) for [Mozilla Firefox](https://addons.mozilla.org/en-US/firefox/addon/keepassxc-browser/) and [Google Chrome or Chromium](https://chrome.google.com/webstore/detail/keepassxc-browser/oboonakemofpalcgghocfoadofidjkkk)
+- Sharing of passwords using KeeShare. See [Using Sharing](./docs/QUICKSTART.md#using-sharing) for more details.
 - Many bug fixes
 
 For a full list of features and changes, read the [CHANGELOG](CHANGELOG) document.