Error details to json

Note: These changes are in an effort to quickly replace the original consumption (e-mail) with a JSON source instead for the error details report.

1. Changed the object structure for the error_details.py JsonReport save to produce a parent/child nested structure for each failed request.
2. Changed to use the environment's STACKTACH_INSTALL_DIR variable when appending to the system path for settings.py and the three reports.
3. Removed summary tables from error_details report. We can add these back later if needed, but they didn't seem to be of much use once the JSON endpoint is available.
4. Changed 'rsp' function to handle data being both a Python list or dictionary, and a JSON representation. The double dumping was causing the JSON to be malformed when requested via stacky_server.py