Add combination compartments

[ma3ke]

Combine different compartments from the input configuration.

For instance, this would allow us to combine an analytical sphere compartment that is created when the configuration is loaded with a mask that is loaded from an npz file.

I think that this does warrant a better syntax, as I'm currently relying on deserialization of the json to give the rudimentary syntax tree.

Example input file

Here is the space section of an input file that uses this ability.

	"space": {
		"size": [153.0, 142.0, 148.0],
		"resolution": 0.5,
		"compartments": [
			{
				"id": "droplet",
				"analytical": {
					"shape": "spherical"
				}
			},
			{
				"id": "outside_virion",
				"voxels": {
					"path": "masks/outside.npz"
				}
			},
			{
				"id": "outside",
				"combination": [{ "or": [ 
					{ "id": "outside_virion" }, 
					{ "id": "droplet" } 
				]}]
			},
			{
				"id": "inside",
				"voxels": {
					"path": "masks/inside.npz"
				}
			},
			{
				"id": "m_proteins",
				"voxels": {
					"path": "masks/m_proteins.npz"
				}
			}
		]
	}

Note that I think that I may currently have the or and and directives flipped around, because this expression for the outside combination compartment seems rather silly.

That is to be addressed before this PR merges.

[ma3ke]

The example config above is part of a setup to create the following example system.

This is not final, but just placing it here to help communicating the change.

[ma3ke]

I think that we want a proper and and xor combinator in here as well.

[ma3ke]

The code duplication in the above section screams for refactoring.