v0.3.0: Improved ribbon

The ribbon is the top bar of a note, with different options such as "Basic Properties", "Owned attributes", "Inherited attributes", etc. In order to make these options appear more KDE-like, they were moved to the bottom of the editor, similar to how the Kate editor handles this.

In order to achieve a visual balance, the "Note revisions" and context menu were kept at the top, moved near the "Create new split" button.