Support for requesting, receiving and setting profile pictures.

I didn't test it very much because of lack of time and also needs a good review and possibly various changes.
I will not be able to test it or work on it until next week so I preferred to create the pull request now in case it is useful as a starting point at least.
If you need me to do more changes before accepting it let me know and I will try my best on monday 29 december.
Thanks!!!