Adding Friends to Players

**Describe the solution you'd like**
As a user of playfabbuddy, I want to be able to either create new users with friends or add friends to already existing users.

```
playfabbuddy player add friends PLAYERS_TO_ADD_FRIENDS_TO FRIENDS_TO_ADD
```

PLAYER_TO_ADD_FRIENDS_TO
This could be either be the locally managed player file of playfabbuddy, or it can be a player segment.

FRIENDS_TO_ADD
This needs to be a list of players that are added to every PLAYERS_TO_ADD_FRIENDS_TO. An important note is that this should be bidirectional, so FRIENDS_TO_ADD should add the player as friend they got added to.