Add friend

[smithe0]

Added functionality to add a friend. Friends page now actually displays friends rather than every user.

Notes:

• You cannot remove friends yet.
• Duplicates ARE checked for and cannot be added as friends.
• Overwrote equals and hashcode methods for user. Assumes userID is unique and therefore sufficient to be equal.
• removed redundant line in friends list code. (user list loaded from file twice)