Added dynamic namespacing to mapState, mapGetters, mapActions

[Stumblor]

Based on this issue #863, I was also struggling to apply a dynamic namespace to a component that could be used anywhere in the component tree. To support the namespace being applied to a component via the props, I added functionality for the namespace to be supplied as a function.

Example usage:

    var namespace_def = "settings/someModule/";

    module.exports = {
        props: [ "namespace" ],
        computed: mapState((self) => self.namespace || namespace_def, [
            'options', 
            'items'
        ]),
        methods: mapActions((self) => self.namespace || namespace_def, [
            'SomeAction', 
            'AnotherAction'
        ])
     };

[ktsn]

IMO, it would be better to use function-style mapper described on this comment instead of introducing dynamic namespace.
Because the latter declares the component computed/methods dynamically. It would make harder to type check statically and grasp the component behavior.

[Stumblor]

That's true, but it's at the expense of a more verbose declaration. I can see this becoming more of a problem will large numbers of methods / properties.

Couldn't the type checking be done after the function was resolved?

[Stumblor]

Ok - I'm coming around more to this way of thinking. Going to close this now.