First very buggy implementation of media encryption

Known bugs:
 * download of encrypted media remains stuck in sQueue
 * downloading the same media a second time does not decrypt it

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
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>
Merge branch 'master' into audio_message