HPCC-8794 Handle ESP Exceptions

Provide visual feed back for ESP exceptions and failed calls.
Enable cross site calls (will need dojo 1.8.4 fix).

Fixes HPCC-8794

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
HPCC-8583 Make ESPWorkunit a singleton to support MVC paradigm

Fixes HPCC-8583

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #4012 from GordonSmith/HPCC-8583

Make ESPWorkunit a singleton to support MVC paradigm

Reviewed-By: Miguel Vazquez <miguel.vazquez@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>