Enhance editor menu usability

The usability of the editor was enhanced very much for translators and reviewers in the normal and details view mode of the editor. The action icons to handle the currently open segment were moved to the top. Same for the special characters. Users can now select, what icons they want to have in the top toolbar and what in a drop-down list. The repetition editor settings were moved to the left into the "view modes" drop-down, which was renamed to "settings". In the right panel the terminology was moved to its own tab and the segment meta data tab was renamed to "Quality assurance". As a result there is much more space for terminology and QA in the right panel.