Amend get_next

[ryanbdclark]

Amend the get_next function which calls /Shows/NextUp to include an optional seriesid and userid parameter.

This will allow you to retrieve the next up just for a specific series rather than all series, as well as getting the next up for a specific user rather than being limited to the user currently logged in.

Before I go down a rabbit hole with this as I have more changes I'd like to make. What's your opinion about allowing the user to specify a userid in the request rather than always using the current logged in user? I feel as an admin user logged in I should be able to retrieve information about any user rather than just the user I am logged in as. If you can already do this and I've missed it then let me know.