Updated Testing Info. Ready for PR.

Major documentation cleanup and update.
- Fixes Issue #1557
- Moves entire documentation to Markdown format. Much simpler.
- Fully supports Doxygen 1.8.7+
- All documentation targets updated: user_doc, share/man, doc and
doc/refman.pdf.
- Tested across Ubuntu, CentOS and Mac OS.

See doc_src/FORMATTING.md for in depth rationale and style guide.