The friction property is name collision_friction in TileMap

[Chais]

Godot version:
master (3a5b25d as of writing this)

OS/device including version:
Linux 4.15.15

Issue description:
The friction property is named collision_friction in the TileMap class. But only there. RigidBody2D and StaticBody2D for example just use friction. This necessitates unsightly constructions like this:

var friction = 0.8
if collision:
	if collision.collider.name == "TileMap":
		friction = collision.collider.collision_friction
	else:
		friction = collision.collider.friction

Or any other method of determining the type of the collider.

[akien-mga]

This is now kept track of in #16863, so closing.