This avoids the need for liquid templates to the latest version.
Signed-off-by: Mark Lodato <lodato@google.com>

Signed-off-by: Mark Lodato <lodato@google.com>

Similar to e56c3889

 (#270), but for the list of subpages in
/spec/v0.1/index. This change replace the "automatic" code with a manual
list, which is much easier to understand and maintain.

No content change. The only HTML change is to switch from absolute to
relative links and to eliminate empty `<li>` elements.

NOTE: Neither the original nor new code correctly handled displaying
more than one specification version. This commit adds a TODO making it
clear that it doesn't work.
Signed-off-by: Mark Lodato <lodato@google.com>

The old nav system had several drawbacks:

- It tried to "automatically" list all of the specification pages using
  the `order` field of each page, but this didn't work correctly and was
  a pain to maintain. Plus the liquid code was complicated.
- There was no way to customize the link text (always page title) or to
  link to custom URLs (e.g. /provenance instead of /provenance/v0.2).
- The mobile and non-mobile templates were duplicate but slightly
  different, which may lead to bugs in the future.

Now we have an explicit configuration in _data/nav.yml and use the same
template for both mobile and non-mobile nav bars. This should be easier
to maintain.
Signed-off-by: Mark Lodato <lodato@google.com>

This fixes the pages when rendered on GitHub and generally makes
the source easier to read.
Signed-off-by: Mark Lodato <lodato@google.com>

Signed-off-by: Dev Morgan <disfordisford@gmail.com>