Add header comments to telepathy-kdeconnect

Summary:
Add header comments to Presence methods

Add header comment to curious 'messageReceived' signal

Add .arcconfig

Change plugin's reported name from telepathy-morse to telepathy-kdeconnect

Reviewers: kdeconnect, apol, davidedmundson

Reviewed By: apol

Differential Revision: https://phabricator.kde.org/D5921