Add the ability to stack presets and or modify properties from an animation preset

[0neGal]

Currently animation presets are limited to simply applying animation properties, and each preset can have some settings/knobs/placeholders, but there's no way to then set extra properties on top of these presets, nor is there a way to only override parts of a preset.

Effectively what I'm asking for is for something like this to work:

animations = ({
	triggers = [ "close", "hide" ];

	preset = "slide-out";

	duration = 0.2;
	direction = "down";

	opacity = {
		end = 0;
		start = 1;
		duration = "duration";
	}
})

Currently the extra properties aren't being used, and it instead only uses the properties set by the preset, same with setting properties that exist in the preset.

Adding this would be able to significantly simplify config files, especially together with #1320