Previews for text, images, and possibly videos

[bain3]

Add an option to preview the file if it is a known type (determined from extension)

[practicingman]

Add an option to preview the file if it is a known type (determined from extension)

how previews can be done if files are encrypted?

[bain3]

The previews are done after the file is downloaded and decrypted. For example people don't usually want to download jpegs, they just want to look at it. It is partially implemented for images right now.