Switch to standard underscore escaping

We used an underscore-autoscape extension/monkeypatch from back in the
day before underscore supported escaping.  But several versions ago,
underscore added Unfortunately, the escaping.

Unfortunately, extension's syntax was the exact reverse of the syntax
underscore now uses:

    <%- "<script>" %> yields &lt;script&gt;
    <%= "<script>" %> yields <script>

So, after removing our shim, go through and reverse the = vs - on all of
our templates.