changing username by admin

[soonahn]

Addresses #698

[geekgonecrazy]

This also looks solid. Going to test both this and #696. The underlying method hasn't been tested fully.

[engelgabriel]

Guys, update the username is not that simple. You need to use the method. There are a lot of checking and references that need o be updated together, not just the users collection.

[engelgabriel]

Need to call /packages/rocketchat-lib/server/methods/setUsername.coffee

[soonahn]

Updated so the update method is only called once. New to meteor, didn't realise that was possible. Thanks!

[engelgabriel]

I think this should be done, but using the right method call

[soonahn]

@engelgabriel fixed to use the setUsername method.