Add support for recommendations

[jpdillingham]

First, add support for liked/hated lists:

• Add liked interest (InterestAdd/51) via AddLikedInterestAsync(string interest)
• Remove liked interest (InterestRemove/52) via RemoveLikedInterestAsync(string interest)
• Add hated interest (HatedInterestAdd/117) via AddHatedInterestAsync(string interest)
• Remove hated interest (HatedInterestRemove/118) via RemoveHatedInterestAsync(string interest)

Add the ability to retrieve user interests:

• Get user interests (GetUserInterests/57) via GetUserInterestsAsync(string username)

There doesn't seem to be a way to retrieve your own interests; consider whether adding GetInterestsAsync() should return a fetch using the currently logged in username.

Add the ability to fetch recommendations:

• Get recommendations (GetRecommendations/54) via GetRecommendationsAsync()
• Get global recommendations (GetGlobalRecommendations/56) via GetGlobalRecommendationsAsync()
• Get item recommendations (GetItemRecommendations/111) via GetItemRecommendationsAsync(string item)

Add the ability to fetch similar users:

• Get similar users (GetSimilarUsers/110) via GetSimilarUsersAsync()
• Get item similar users (GetItemSimilarUsers/112) via GetItemSimilarUsersAsync(string item)

[jpdillingham]

This is no longer on the roadmap. The feature is deprecated in Soulseek Qt and I don't think this brings enough value to warrant the development effort at this time.

[jpdillingham]

This would still be a great first issue for someone looking to gain familiarity with the library, however.