Todo:
This is a list of improvements I still want the add, in no particular order.
Add updated and user column to all tables to record last changes.
Allow Create/Edit property classes.
Allow Create/Edit issue types.
Allow Create/Edit issue status and display order.
Allow file uploads with issues.
Allow setting a not-shared property to shared.
Allow setting a shared property to not-shared if it is not used by other objects.
Allow users to change their passwords.
Create an installer that prepares the database for initial use.
Create upgrade paths for newer versions so older data can be conserved. Done
Help functions on every page.
Create backup and restore options.
Better reporting based on values in properties.
Import/Export database to spreadsheet, csv, sql, ...
Logging. (Log every SQL query and the user that ran the query)
Delete objects, properties, types and relations if not used.
Add object composition, an object can consist of multiple other objects.
Use OOP and make the code easier to maintain.