added preview for files that can be shown through the system
added preview for files that can be shown through the system

UH-CI/uh-togo-angular-filemanager,UH-CI/uh-togo-angular-filemanager,UH-CI/uh-togo-angular-filemanager,UH-CI/uh-togo-angular-filemanager,UH-CI/uh-togo-angular-filemanager