Clean up footer: fix copyright, move GitHub link out of the nav (#41)

- Copyright was "© <year> <name>" where <name> is conf.name — an
  operator-configurable display name (e.g. whatever CFG_ORG is set
  to), not a real copyright holder. Changed to "© <year> theta42",
  matching the LICENSE file. Also dropped "All rights reserved",
  which contradicts the MIT license this project ships under; added
  an explicit MIT License link instead.
- Moved the GitHub icon link out of the top nav (where it competed
  with actual navigation items) and into the footer, alongside the
  license link and version/build info.
- Deduplicated the identical buildVersion/buildHash/buildYear
  computation that was copy-pasted in both routes/index.js and
  routes/oauth.js into a shared nodejs/utils/build_info.js.

Verified by rendering top+bottom with the real ejs package: no
template errors, GitHub link present exactly once (in the footer,
not the nav), "All rights reserved" gone, MIT License link present.
npm test failures (155) are pre-existing/environmental (no LDAP
server here) — identical failure count with these changes stashed
out.

nodejs/views/top.ejs

@@ -86,11 +86,6 @@
   	          Admin
   	        </a>
   	      </li>
-  	      <li class="nav-item">
-  	        <a class="nav-link" href="https://github.com/theta42/sso-manager-node" target="_blank">
-  	          <i class="fa-brands fa-github"></i>
-  	        </a>
-  	      </li>
   	    </ul>
   	    <div class="form-inline mt-2 mt-md-0">
   	      <a id="cl-login-button" class="btn btn-outline-danger my-2 my-sm-0" onclick="app.auth.forceLogin()" style="display: none;">