Channel.private flag

[rakiru]

Just a simple boolean flag should do, but some more thought should be given before implementing.

This could be used by things such as web to only show non-private channels on its channel list, or for the factoids web view to only show public-channel factoids. If a user is logged in to web, it should be as simple as checking if user in channel to also display relevant private channels. Note to self: check channels have a public userlist API.

--- Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/27182889-channel-private-flag?utm_campaign=plugin&utm_content=tracker%2F269930&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F269930&utm_medium=issues&utm_source=github).

[gdude2002]

IRC channels do have a users set() and API but it's not in the generic channel - should do that