[refs #8][Godot 3] Add AnimationPlayer import

[Kerberross]

Add the animation player import to godot 3.

The import option contains:

• scale for the sprite
• external save for animation
• external save path for the animation

It also:

• use the fps stored in the pxo file for animation instead of an import parameter
• add default project settings for import parameter and default import type

More details in https://github.com/Technohacker/godot_pixelorama_importer/issues/8