V2 - modular accessors

[dxinteractive]

Split out type-based parcel methods and actions so adding support for new data types is modular.
Also remove as much unmutable as possible from the core library

export const array = (parcel) => ({
    when: Array.isArray(parcel.value),
    getters: {
        isIndexed: () => true
    },
    methods: {
        push: (...values) => ['push', values],
        pop: () => parcel.get(-1).delete()
    },
    actions: {
        push: (data, values) => data.concat(values) // how to handle child?
    }
});

export const arrayChild = (parcel) => ({
    when: Array.isArray(parcel._parent),
    always: true,
    child: true,
    getters: {
        isElement: () => true,
        isFirstChild: () => {},
        isOnlyChild: () => {}
    },
    methods: {
        swapNext: () => ['swapNext']
    },
    actions: {
        swapNext: (data, lastKey, values) => { ... }
    }
})