- Users table model renamed to UsersTableModel- causes linker conflict

with class TableModel in accomodation plugin.
- Edit record dialog is now screen centered.
- Plugin tabs in application main window are now closable.

application/mainwindow.cpp

@@ -63,3 +63,8 @@ void MainWindow::on_actionOpen_database_triggered()
     dialog.setWindowTitle(tr("Open Database"));
     Context::instance().openDb(dialog.getOpenFileName());
 }
+
+void MainWindow::on_tabWidget_tabCloseRequested(int index)
+{
+    ui->tabWidget->removeTab(index);
+}