urls: Route /error/NNN/ to static.views.handler.

Since our Apache configuration uses `ErrorDocument NNN /error/NNN/`,
this is necessary to return the correct status code in those cases.

static: Re-fix path manipulation in index.

* Strip any leading / to treat it as a relative path.
* Append `index.html` before converting to bytes.

Avoid query string passed along in rendering.

This middleware is a bit of a mess anyway, since it's basically using
static files as templates. However, we definitely don't want to add any
GET query parameters rendered into the path name.

Add sitefundgoal to top level view context.

The base template now has access to the fund-raising goal that will be
displayed site-wide. The view here must provide it in the context for
access everywhere.

Furthermore, we need a local context processor to make sure it's in
context everywhere, and we have to make sure that context is properly
passed along.

This code is a bit cargo-culted in, based on what I read in various
places about adding the Request context.

Rework to simply call with new kwargs.

Redo call so that I just get my own at call time.

Rework fundgoal lookup urls data.

The urls.py is of course only evaluated once: at Apache load time, which
means the data in the template became stale and is not dynamic.

This change should cause the lookup to happen at each page view.

Fundraising goal lookup for template: 1st attempt

This seems to be the best approach to pass a fundraising goal record to
a template. While the static hack that tmarble implemented probably
needs work anyway, this is probably the best way currently to interface
certain general data that we seek to place on many different pages
through the templates.

I looked into a templatetags solution, but this seemed more
straightforward and more fitting with Django principles (I think :).