Varie

• fixed spurious border for pdf and png plots;
• Maintenance of Plotsettings dialog continued (SS-3564);
• Tooltips in Plotsettings dialog completed;
• Refactoring;
• Layout of Variables tab in Plotsetting dialog simplified;
• Definition of canvas variables fixed (SS-3463);
• Simplify number editing in plot settings dialog (SS-3564);
• Range checking for log plots implemented;
• Mouse-zoom of log plots corrected (SS-3565);
• Fixed missing border information when cloning draw region;
• Fixed storage of border state (SS-196).