Image Validation

[satyajit-patil]

Summary: User can upload a non-image file to flash
Description: I was able to upload a non-image file (ex. doc, executable, etc.) and flash it without getting a warning. I was able to produce this bug on a windows machine. This does not seem to be an issue on a Mac; on a Mac, the user can only upload '.bin' files.
Severity: Trivial
Suggestions: Upon uploading a file, you may need to validate that the file is the correct format (an image).