Make man page translatable and conform to general KDE docs structure

Summary: It is impossible now to translate man page, it is separated from the other docs and that is non-logical.

Test Plan: Compiles, man page installs as expected, can be translated, conforms to the general KDE man page structure.

Reviewers: #labplot, #documentation, sgerlach

Reviewed By: #labplot, sgerlach

Subscribers: sgerlach, kde-edu, kde-doc-english

Tags: #kde_edu, #documentation

Differential Revision: https://phabricator.kde.org/D17772