Save button suggestion

Originally from here: https://forum.turris.cz/t/reforis-save-button-suggestion/13672

Some reForis pages are very long. Having the [SAVE] button at the bottom means it is neither visible nor accessible without much scrolling.

A more user-friendly design would add a pair of buttons in the left hand menu beneath About. Normally these buttons would be invisible. Once the current page gets modified the buttons would appear: [SAVE CHANGES] and [DISCARD CHANGES].