refactor: Switch to 'map-like object keyed by string and type vector' format

See https://code.studioinfinity.org/glen/nanomath/wiki/Item-Specifications.
  Also stubs out the TypeDispatcher, mocking the merge function, so we
  can see that all of the proper things will be added.

  Ready for initial implementation of the TypeDispatcher.

src/number/Number.js

@@ -1,3 +1,3 @@
-export const Number = {
-   test: n => typeof n === 'number'
-}
+import {Type} from '../core/Type.js'
+
+export const Number = new Type(n => typeof n === 'number')

src/number/arithmetic.js

@@ -1,4 +1,4 @@
-import {plain} from './tools.js'
+import {plain} from './helpers.js'
 
 export const abs = plain(Math.abs)
 export const absquare = plain(a => a*a)

src/number/helpers.js

@@ -0,0 +1,5 @@
+import {Returns, onType} from '../core/helpers.js'
+import {Number} from './Number.js'
+
+export const plain = f => onType(
+   Array(f.length).fill(Number), Returns(Number, f))

src/number/tools.js

@@ -1,4 +0,0 @@
-import {Number} from "./Number.js"
-
-export const plain = f =>
-   [Array(f.length).fill(Number), {returns: Number, behavior: f}]

src/number/type.js

@@ -1,4 +1,4 @@
-import {plain} from './tools.js'
+import {plain} from './helpers.js'
 
 // Not much to do so far when there is only one type
 export const number = plain(a => a)

src/number/utils.js

@@ -1,3 +1,3 @@
-import {plain} from './tools.js'
+import {plain} from './helpers.js'
 
 export const clone = plain(a => a)