Feat/remove dash app

[pdmnyberg]

This PR closes #52 and #66

It will:

• Remove metrics middleware to simplify system structure
• Remove dash dependency
• Remove pandas and numpy dependency
• Calculate metrics using SQL and standard python instead of pandas/numpy
• Move plotly scripts into repository in order to make the system properly standalone
• Change download functionality to download the entire metrics result for the current superset

To test:

• start development environment
• make sure the world map works as expected
• make sure the metrics filtering works as expected
• make sure the download, on the metrics pages, work as expected