Better plugin check

Summary:

• Clean up plugin search.
• Runtime insert of binary path/plugins
• check all paths for plugins and use the newest set found
• update docs

Signed-off-by: Chris Rizzitello <rizzitello@kde.org>

Reviewers: Atelier: AtCore, tcanabrava, laysrodrigues

Reviewed By: Atelier: AtCore, tcanabrava, laysrodrigues

Subscribers: Atelier: AtCore

Tags: Atelier: AtCore

Differential Revision: https://phabricator.kde.org/D13345