File Metadata #178

Write code to handle file metadata. 4 options, choose at upload time:

1. wipe all metadata (how to do this?)
2. wipe all metadata except camera technical data (shutter speed etc) (how to do this?)
3. wipe all metadata except camera technical data (shutter speed etc) and GPS info (how to do this?)
4. do not touch metadata (this is what BMA does now)