Add Ekos docs to KStars

Summary: Ekos docs by Jasem Mutlaq (converted by his permission), screenshots and video from the StellarMate site.

Test Plan: checkXML5, meinproc5, and PDF conversion works fine.

Reviewers: #documentation, #kstars, mutlaqja

Reviewed By: #kstars, mutlaqja

Subscribers: kde-edu, kde-doc-english

Tags: #kde_edu, #documentation

Differential Revision: https://phabricator.kde.org/D18335