Modify avatar recommendations
test_avatars: Implement new policy for the user avatar file

Change location of the user avatar from "<data dir>/avatar.png" to
"<data dir>/avatars/<user id>.png", as proposed by commit
6f4ab49f5c2a33aab00bdb9e80dfe51624089899
Merge branch 'master' of https://github.com/irungentoo/toxcore
change avatar requirements
Merge branch 'master' of https://github.com/dubslow/toxcore