Factory returns not the same as the class

[Falke-Design]

new L.Point() has a different result as L.point().

I didn't checked all factories , but same behavior in:

• Bounds
• Point
• LatLng
  https://plnkr.co/edit/bfWXNSffczjx9Lsp

Mostly in the factory is the part:

if (x === undefined || x === null) {
	return x;
}

I suggest to remove this checks. What do you think?

[johnd0e]

Related: #7128, #7767