Window: organize and scope properties

[danirabbit]

So we know what our API is here

• public signals and properties at the top
• Explicitly scope things (no implicit private)
• make tab_view private set
• Scope down widgets that don't need public access

[jeremypw]

Is this ordering mentioned in the developer docs? I was never sure what the approved order was.

[danirabbit]

@jeremypw i don't think it is documented. More just convention. I'll put together a proposal!