code: public boolean addElement(P element) {
  		boolean changed = false;
  		if (element != null) {
  			final GridCellElement<P> gridElement = new GridCellElement<>(element);
  			for (final GridCell<P> cell : getGridCellsOn(element.getGeoLocation().toBounds2D(), true)) {
  				if (cell.addElement(gridElement)) {
  					changed = true;
  				}
  			}
  		}
  		if (changed) {
  			++this.elementCount;
  		}
  		return changed;
  	}
docs: Add the element in the grid.
  
  @param element the element.
  @return <code>true</code> if the element was added;
  otherwise <code>false</code>.