Added new page "Statistics" to the Database Settings dialog that shows information like number of groups and entries, number of unique and re-used passwords, average password length, etc.
Show warnings for problematic values with explainations for the user in tooltips.
Fixes#2034
Database statistics icon:
Downloaded from: https://www.flaticon.com/authors/freepik
Original source: https://www.flaticon.com/free-icon/bars-chart_265733
