Eliminate base_standard.html template and internalNavigate blocks

The base_standard.html template was an unnecessary level of template
inheritance.

Also removed unused `min` and `subtract` template tags.

Move fundraiser calculations to model

This changes simplifies the template and adds correct pluralisation of
hours/hour remaining.

Display donation bar, noting it's results, for 1 week after end

The fundgoal section is now always included, but an if statement now
wraps the entire (partial) file, which will only generate any content
if it's not more than one week after the fundraiser has ended.

Add an else that indicates these are results if it is past the end of
the fundraiser.

Calculate hours when only one day is left.

This {% widthratio %} trick is something I found online that didn't
require a django-math module to work, but I would have rather written
something that:

(b) Could have a different message when there is only one hour
left: “less than one hour left” (i.e., tested if hours == 1)

(c) Will say “hour” instead of “hours” when there is exactly 1 hour
left.