Structure into modules

[bastianilso]

The ArduinoLoggerShiny app is messy, and we need a better structure.
It would be good to get modularized code in here.

Check out the structure of the r shiny demo application.

• Each page should be a module
• Each category should be a module
• Each plot should be its own module.
• The Participant selection and e-mail selection should be each their own modules.
• A data import module which takes care of loading the data.

Please provide a drawing of how these will interface.