Change how users delete entries from the database

Add a button to delete a row from the data table. This deletion can be reverted until the changes are saved to the database. Because we changed the way entries are deleted, a popup now asks user to confirms that they want to save changes to the database.

This merge request only changes the way the user deletes an entry from the database. It does not fix any problem covered by #189 (closed).

Implement part of #196 (closed) because some of the functionalities there is required for this merge request.

sohstationviewer/view/db_config/db_config_dialog.py

@@ -621,8 +621,8 @@ class UiDBInfoDialog(OneWindowAtATimeDialog):
         remain unchanged, else self.reset_row_inputs() will be called to reset
         the row.
 
-        :param need_confirmation: whether this method is called on the dialog
-        being closed
+        :param need_confirmation: whether confirmation is needed before saving
+            the changes made to the database
         """
         # try:
         #     self.data_table_widget.focusWidget().clearFocus()