model: added visitor pattern to Area
model: added SizeCalculatorAreaVisitor
model: added visitor pattern to Location
model: renamed asString to toString in Location
model: added some doc to Location
model: added GpsLocationAdapter
model: renamed SizeCalculatorAreaVisitor to AreaCalculator
model: added CompositeArea
model: added Iterable "role" to CompositeArea
model: added composite area calculation to AreaCalculator
model: added jackson annotations to CompositeArea