Bugfixes for 3.8.4 (new asset system, crashes etc.)

- Image loader now closes the streams
- Proper handling for objects registry
- Added initial basic support for models and shaders
- Reduced noise in logging
- Log.f3() now adds small indent
- Added copy button to crash report dialog
- Asset extracting log window now auto-closes on success
- New icons, dropped 32px tree, improved icon loader