Separated web and rest programmatic-api, build + web-interface bug fixes

This release encompasses issues pertaining to milestone 0.6.1.

This short milestone has been motivated by the following bugs:

• web-interface, returned 500 http errors, upon generating a model, using uploaded json dataset(s)
• web-interface not properly logging into designated flask.log
• libssl-dev package broke, during build, since minor version gets updated frequently
• existing bagr datasets, incorrectly use classification style values

Along the way of squashing the above, the following enhancements were made:

• views.py has been split, to allow different flask blueprint implementations
  • views_web.py
  • views_api.py
• two separate nginx reverse proxies regulate the gunicorn webservers
  • web-interface
  • rest programmatic-api
• rest programmatic-api now requires all routes (except /login) to submit a valid token
  • existing unit tests have been updated respectively
• corresponding README.md, as well as existing documentation have been updated