They are just typedefs for the Selector widget. The API is kind of
messed up and this commit is part of the process of cleaning it up:
right now to use this, you check the is_done() method which if returns
true, the done() method executes the closure you defined when creating
the widget. The closure returns a UIEvent which you can forward
application-wide by context.replies.push_back(event) or handle it in
process_event() immediately.
Merge ui crate with root crate.
In preparation for uploading `meli` as a separate crate on crates.io.
Workspace crates will need to be published as well and having a separate
`ui` crate and binary perhaps doesn't make sense anymore.
Manos Pitsidianakis