Refactor to a more responsive app

[bardram]

The overall software architecture needs to be refactored to create a more simple and reactive app. Things to look at are:

• [x] add linter and fix lnter problems
• [ ] introduce real model objects
• [x] simplify BLoc code
• [x] introduce ChangeNofifier
• [x] better use of ListenerBuilders, FutureBuilder etc.
• [x] cleanup in different state enums

[bardram]

Have decided to not make real models as for now - the sensing and bloc works fine.