Add AsciiDoc versions of the Specification and TCK Licenses to /legal

We've recently updated the Eclipse Foundation Specification License and Eclipse Foundation Specification License.

We need to have AsciiDoc versions of these (specification projects include the license text in their specification documents).

We currently have AsciiDoc version of these here:

• https://www.eclipse.org/legal/adoc/efsl-1.0.adoc
• https://www.eclipse.org/legal/adoc/eftl-1.0.adoc

We should retain the 1.0 versions.

Let's add the AsciiDoc form of the new versions of these licenses alongside the old ones.

Let's also add a means of navigating from the HTML versions to these AsciiDoc versions.

I don't have AsciiDoc versions myself; I believe that they'll have to be created.

/cc @scorbett