Add templates for Akonadi resource and serializer plugins
Summary:
Overhauled versions of the templates from kapptemplate.
Keeping the template with the sources they are based on
helps both discovery and also maintenance.
Reviewers: mlaurent, dvratil
Reviewed By: mlaurent
Subscribers: KDE PIM
Tags: KDE PIM
Differential Revision: https://phabricator.kde.org/D8537