Attempt to prevent title text overlapping with the header image (though second line sits behind the menu...)

This is required because Flask is forcing (via 301) / to be appended to the url
which previously resulted in no rule matching legacy pages. We could disable
strict_slashes to fix this, but it might cause issues elsewhere.

This is required because "site/" was removed from the urls, but a little backend
trickery is usually necessary to get the urls looking right ^_^

This increases the speed of the site by not requiring the site and blog code to
be imported on every request - just those that are relevant. It also splits the
code into modules which are easier to work with.

It seems that Werkzeug doesn't get confused between /en/blog/ and /en/<path:page>

AFAICT these attributes are meant to be on <link> tags, but it shouldn't hurt
having them here instead (though if it doesn't help and <link> tags need to be
added, then this commit should probably be reverted).