PGPCoder: use buffered read/write

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Fix redownload encrypted media

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Use a different notification during media decryption (might take a while)

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>