Implement Software Upgrade Management API and Frontend Functionality

- Added software.php for managing software versions, including download and purchase actions.
- Created upgrade_paths.php for handling upgrade paths management.
- Developed user_licenses.php for managing user licenses.
- Introduced version_access_rules.php for managing access rules for software versions.
- Implemented frontend functions in functions.js for interacting with the software upgrade API.
- Added version_access.php for user access validation and license management.
- Created upgrades.php for displaying available upgrades and handling user interactions.
- Enhanced UI with responsive design and progress indicators for downloads and purchases.

settings/translations/translations_NL.php

@@ -27,6 +27,7 @@ $menu_report_contracts_billing = 'Contracten';
 $menu_report_usage = 'Systeemgebruik';
 $menu_maintenance = 'Maintenance';
 $menu_profiles = 'Profielen';
+$menu_upgrades = 'Software Upgrades';
 $tab1 = 'Algemeen';
 $tab2 = 'Hierarchy';
 $tab3 = 'Log';