Create new DB models for storing parsed histogram files about mlplayground

[nothingface0]

histogram_file_manager app.

• Parse histogram files (CSV format, nanoDQM too in the future) for runs and lumisections
• Store histogram data inside the DB as arrays. This means it will interact with LumisectionHistos2DTable, LumisectionHistos1DTable and RunHisto table.
• Expose progress of parsing on separate view with own URLs. This will require it to have a simple API to allow periodically updating the front-end via AJAX calls.
• List files available in the EOS storage (maybe via a management command?)
• The user/admin should be able to issue commands to start parsing one/many of the available (partially) unparsed files.
  • Easy difficulty: management command which triggers parsing script
  • Medium difficulty: make API allow POSTing raw data from third-party apps which do the parsing. This functionality should be placed inside the Lumisection and Run Histogram apps, not in the histogram_file_manager