Preference for quoting identifier mechanism

A new option is added to the SQL tab in Preferences for choosing which
quoting characters must be used by the application when it inserts an
identifier in SQL code. The three options supported by SQLite are
available.

Default quoting characters have been changed from `Grave accents` to
"Double quotes" (SQL standard).

This options also affect the highlighting of double quoted strings: when
the SQL standard is selected, double quoted expressions are highlighted as
identifiers, otherwise as literal strings.

src/MainWindow.cpp

@@ -1990,6 +1990,8 @@ void MainWindow::reloadSettings()
 
     // Reload remote dock settings
     remoteDock->reloadSettings();
+
+    sqlb::setIdentifierQuoting(static_cast<sqlb::escapeQuoting>(Settings::getValue("editor", "identifier_quotes").toInt()));
 }
 
 void MainWindow::checkNewVersion(const QString& versionstring, const QString& url)