Summary:
Don't use QDBusConnection::ExportAllContents
No need to make connect and receivedPackage public slots (they're are the
parent's already)
Fixes T4975
Test Plan: Rough manual test
Reviewers: #kde_connect, albertvaka
Reviewed By: #kde_connect, albertvaka
Maniphest Tasks: T4975
Differential Revision: https://phabricator.kde.org/D3871
Eavesdrop on the Notify call of the org.freedesktop.Notifications
dbus-interface, proxy all caught notifications to our peer device and
track them in the internal notifications-list.
Also fix "cancel" requests from peer devices, by cutting of
kdeconnect-android's id-prefix.
