refactoring

src/blueprints/Devices.py

src/blueprints/Measurements.py

src/blueprints/Sensors.py

src/logic/database/Database.py

src/logic/database/DatabaseAccess.py

src/logic/database/DeviceAccess.py

src/logic/database/MeasurementAccess.py

src/logic/database/SensorAccess.py

src/logic/database/__init__.py