Feature/background work (#293)

* Background work quick fix

* Formatting

* Background work improved

* Formatting

* Refactoring

* Refactoring

* Allow background data usage

* Added isBackgroundRestricted

* One timer for background and manual update
Removed data saver check for background check

* Removed separate timer for manual update button

* Refactoring

* Merge remote-tracking branch 'origin/dev' into feature/background-work

# Conflicts:
#	Corona-Warn-App/src/main/res/layout/fragment_risk_details.xml

Co-authored-by: Jakob Möller <jakob.moeller@sap.com>