Extended OnlineClient information variables

[bdeb1337]

Hello,

First off thank you for this great library, which is working great for a project of mine.

I was having somewhat the same request as @30 of wanting to expand the basic clientlist command. I've read the latest serverquery documentation that ships with ts3 server version 3.13.7 and included all parameters regarding this command:

I haven't included servergroups yet, since trying to map it as a []int didn't immediately work. I guess it would have something to do with helpers.go line 74 which states // TODO(steve): support groups but I could be wrong. If you are OK with this I could try to give it a go later in a separate pull request? I feel like it might be a little much for one PR otherwise and I could use some guidance in the right direction for that change.

Kind regards

Bob

[bdeb1337]

Opening PR on a branch.