Major update #2

* Finished implementing file property caching system
* Large folders take noticeably longer to load the first time, but are much faster afterwards
* Fixed some PNG files not getting thumbnails
* Thumbnails are now also cached
* Added subtitles to file list entries, which contain file type and size
* Used appropriate cell styles for stat views
* Added formatting of file sizes and display of user names to stat views
* Various minor fixes and improvements