* Mark database dirty if saving fails
* Restore database file from backup if unsafe save fails between deleting database file and copying temporary file into place
* Improve error message display for opening and saving database files
* Do not automatically retry saving after failure. This prevents deletion of the backup database file and improves user awareness of issues.
Use nullptr instead of 0 or NULL to initialize a null pointer. In some
cases, readability was enhanced by replacing 0 with more meaningful
values according to the type of the pointer being initialized.
Chnage to one method to set MessageWidget text passing type as
parameter.
Only messages with questions requiring user input reamin using
MessageBox dialog.
Use signal/slots to set message in MessageWidget and hide message,
signal/slots only used when required.Maybe need to change all calls to
signals/slots in the future.
