Add "password" property to Models.Video or Models.Privacy

[ImperatorRuscal]

GET https://api.vimeo.com/videos/{video_id} includes the "password" property when the privacy setting is "password", but using this library we can't see that property.

This becomes important if you want to either 1) fetch the password (ex: making a viewer that auto-provides the password) or 2) verify the current password (especially if you just changed it using VimeoClient.UpdateVideoMetadataAsync )

While Vimeo returns this property as an element of the Video object, given the current project layout here I imagine it'd make the most sense as a sub-property under Privacy
(ie: string Video.Privacy.Password(get) ).