For now the widgets are to be grown automatically.  It is mirrored after
the installed structure of the LibreVideoConverter library so follow it please, so you can
do diff on it.

General rule is that anything in gtk/cocoa is pretty much fair game,
there's usually some good reason for stuff in miro.frontends.widgets.

For stuff in LibreVideoConverter namespace, think carefully before adding it, with
the exception if it is utilty functions (which we will further abstract
away) or a base class of a platform impementation (such as player.Player).

Python is dynamically interpreted so it is generally safe to remove
the top-level imports and still have the thing run.

As a convention, please prepend the line with ### when you are removing
something, and when you are adding something add ###XXXMVC on the line
before your first addition.