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/ExportCsvDialog.cpp

@@ -5,12 +5,12 @@
 #include "ExportCsvDialog.h"
 #include "ui_ExportCsvDialog.h"
 #include "sqlitedb.h"
+#include "PreferencesDialog.h"
 
-ExportCsvDialog::ExportCsvDialog(DBBrowserDB* db, const QString& deflocation, QWidget* parent)
+ExportCsvDialog::ExportCsvDialog(DBBrowserDB* db, QWidget* parent)
     : QDialog(parent),
       ui(new Ui::ExportCsvDialog),
-      pdb(db),
-      defaultLocation(deflocation)
+      pdb(db)
 {
     // Create UI
     ui->setupUi(this);
@@ -32,7 +32,7 @@ void ExportCsvDialog::accept()
     QString fileName = QFileDialog::getSaveFileName(
                 this,
                 tr("Choose a filename to export data"),
-                defaultLocation,
+                PreferencesDialog::getSettingsValue("db", "defaultlocation").toString(),
                 tr("Text files(*.csv *.txt)"));
 
     // Only if the user hasn't clicked the cancel button