Replace kaccounts KCM with the one from plasma mobile
Summary: plasma-settings has a QML version of the accounts KCM. Since there's no point in using a separate KCM for dekstop and mobile use it on the desktop as well. Code is a almost direct copy from plasma-settings
Test Plan: Opened KCM. Added a google account
Reviewers: Plasma, bshah, dvratil, ognarb
Reviewed By: Plasma, bshah, ognarb
Subscribers: ognarb
Differential Revision: https://phabricator.kde.org/D24133