Implemented support for "coast visitable" objects:

- objects marked as coast visitable can be visited from land even when
placed in water
- added isBlockedVisitable and isCoastVisitable method to
CGObjectInstance
- implemented json config for these properties in banks

lib/mapObjects/MiscObjects.cpp

@@ -1294,6 +1294,11 @@ CGBoat::CGBoat()
 	layer = EPathfindingLayer::EEPathfindingLayer::SAIL;
 }
 
+bool CGBoat::isCoastVisitable() const
+{
+	return true;
+}
+
 void CGSirens::initObj(CRandomGenerator & rand)
 {
 	blockVisit = true;