[FEATURE] Deep module imports

[CITguy]

As a consumer of HelixUI, I would like to use deep module imports, so that I can import specific functionality from a HelixUI submodule.

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With #309, we have the ability to selectively import items from the helix-ui module. However, we still have to import Elements and Utils as a namespace if we want to use any of the available functionality within them.

A consumer should be able to use the following syntax:

import { HXElement } from 'helix-ui/elements';
import { KEYS } from 'helix-ui/utils';
import { getPosition } from 'helix-ui/utils/position';

[CITguy]

Anticipated consumption after Nov 2018 CAREaTHON project.

import { HXElement } from 'helix-ui/lib/elements';
import { KEYS } from 'helix-ui/lib/utils';
import { getPosition } from 'helix-ui/lib/utils/position';

[CITguy]

We'll be investigating LOE to complete this work.