Before commit 28caabecd, it was clear which budgets were in draft mode
because their phase was "drafting".
Now the phase isn't "drafting" anymore, so we have to make it clear
somehow that the budget is a draft.
I'm using styles similar to the ones we added in commit 2f636eaf7 for
completed budgets but at the same time making them slightly different so
it's easy to differenciate completed and drafting budgets.
We're going to change it a bit, and using a component allows us to use
the `header` method and easily add a title to this page, which lacked
the `<title>` tag.
Previously the draft mode was a phase of the PB, but that had some
limitations.
Now the phase drafting disappears and therefore the PB can have the
status published or not published (in draft mode).
That will give more flexibility in order to navigate through the
different phases and see how it looks for administrators before
publishing the PB and everybody can see.
By default, the PB is always created in draft mode, so it gives you
the flexibility to adjust and modify anything before publishing it.
Note the CSS could probably be improved to avoid duplication with other
button style definitions. However, that's fine because we're going to
change the style of the links soon.
For the same reason, I haven't bothered to style every single link the
way it was until now.
