Documentation updates

* Update date and version numbers
* Remove entities unused
* Add more keywords (without copyright)
* Suitable tags and add some shorcut
* Change http: to https:
* Sync with the GUI
    - Add 'Game -> Save a Solution...'
    - Add 'View -> Full Screen Mode'
    - Reorder the subitems of 'Settings -> Change Theme...'
    - Add KDE Fundamentals reference for Help menu