N1QL to SQL++ Rebrand for JavaScript UDFs

Change N1QL to SQL++ for the JavaScript UDFs module in the docs-server repo.

1. Change N1QL to {sqlpp} in running text
2. Change [source,n1ql] to [source,sqlpp]
3. Do not change n1ql in file names, directory names, extensions, links, or anchors
4. Do not change n1ql in commands, options, UI text, or output text

N.B. This issue does not cover the following:

• The javascript UDF how-to guide is covered by DOC-10446
• The javascript UDF user interface guide is covered by DOC-10447