Bitcoin.pdf: Create Page Linking To Translations

- Adds a new page linking to all translations of Nakamoto's Bitcoin
  paper, and also provides instructions for adding new translations

- Changes all links on the site that used to point directly to the
  English bitcoin.pdf to point to the new page.

- Add Spanish Translation by Breathingdog, as well as Spanish strings
  for the now page also by Breathingdog

_templates/bitcoin-paper.html

@@ -0,0 +1,38 @@
+---
+# This file is licensed under the MIT License (MIT) available on
+# http://opensource.org/licenses/MIT.
+
+layout: base
+id: bitcoin-paper
+---
+<h1>{% translate pagetitle %}</h1>
+<p class="summary">{% translate summary %}</p>
+
+<p>{% translate description %}
+
+{% comment %}
+NOTE: before adding a new file, follow these steps:
+
+1. Make sure it has been uploaded in ODT form to
+   https://github.com/saivann/bitcoinwhitepaper
+
+2. Ask a site maintainer to generate the PDF format from the ODT format.
+
+3. Scan the PDF using VirusTotal.com and post a link to the scan report
+   on GitHub (this provides a sha256sum of the file, so it can be
+   verified that the file was scanned).
+
+The files should be listed in this order: English orginial first; then
+UTF-8 alphabetical order
+{% endcomment %}
+<ul>
+<li><a href="/bitcoin.pdf">English original</a></li>
+
+<li><a href="/files/bitcoin-paper/bitcoin_es.pdf">Español (España)</a> {% translate translated_by %} <a href="https://github.com/breathingdog">Breathingdog</a></li>
+
+<li><a href="/files/bitcoin-paper/bitcoin_es_latam.pdf">Español (Latinoamericano)</a> {% translate translated_by %} <a href="https://github.com/gubatron">Angel León</a></li>
+
+<li><a href="/files/bitcoin-paper/bitcoin_ru.pdf">Русский</a> {% translate translated_by %} <a href="https://github.com/arvicco">Ar Vicco</a></li>
+</ul>
+
+<p>{% translate submit_new_translation %}</p>