Migrate netlify-cms-www site into this repo (#860)

* Add frontmatter to docs files (prep to move)

* Move docs into position for website migration

* Migrate website from netlify-cms-www

Some modifications, including most of the changes in https://github.com/netlify/netlify-cms-www/pull/58 (previously reverted).

Also updated the readme and added hugo-bin for quicker onboarding of new docs contributors.

* Remove netlify.toml

This allows separate build commands for cms-demo and netlifycms.org.

* Remove website/netlify.toml

May re-add later, but it's not doing anything for now.

* Remove unused content file

website/site/layouts/partials/edit-link.html

@@ -0,0 +1,10 @@
+<a class="edit-this-page" href="https://github.com/netlify/netlify-cms/blob/master/website/site/content/{{ .File.Path }}">
+  <svg version="1.1" id="pencil" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
+     width="14px" height="14px" viewBox="0 0 512 512" enable-background="new 0 0 512 512" xml:space="preserve">
+  <path d="M398.875,248.875L172.578,475.187l-22.625-22.625L376.25,226.265L398.875,248.875z M308.375,158.39L82.063,384.687
+    l45.266,45.25L353.625,203.64L308.375,158.39z M263.094,113.125L36.828,339.437l22.625,22.625L285.75,135.765L263.094,113.125z
+     M308.375,67.875L285.719,90.5L421.5,226.265l22.625-22.625L308.375,67.875z M376.25,0L331,45.25l135.75,135.766L512,135.781
+    L376.25,0z M32,453.5V480h26.5L32,453.5 M0,376.25L135.766,512H0V376.25L0,376.25z"/>
+  </svg>
+  Edit this page
+</a>