Move all settings logic to the preferences dialog

Read and write the settings only from the preferences dialog.

Remove all the copies of some settings which were stored in nearly every
dialog class individually.

Simplify the settings dialog code by removing all those not really
needed slots.

src/EditDialog.h

@@ -16,8 +16,6 @@ public:
     explicit EditDialog(QWidget* parent = 0);
     ~EditDialog();
 
-    QString defaultlocation;
-
 public:
     int getCurrentCol() { return curCol; }
     int getCurrentRow() { return curRow; }