HPCC-8604 Add JavaScript Layout

Added experimental version of graphviz layout in JavaScript (via emscripten).

Fixes HPCC-8604
Change instances of <br> to <br/>

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #3855 from GordonSmith/HPCC-8604

HPCC-8604 Add JavaScript layout engine

Reviewed-By: Miguel Vazquez <miguel.vazquez@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>