ENYO-2286: Add samples for core Enyo UI controls

Issue
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We need samples to show the basic UI objects as well as to serve as an onyx-free testbed for those controls.

Fix
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Samples have been added for all of the basic UI controls. The `Audio` sample was also redone (and included in the `Sampler`) to utilize non-Onyx controls. Many of the samples are fairly basic in terms of visuals, with the aim of highlighting functionality and not layering on too much styling that would mask features or obstruct testability (we can progressively add additional styling where needed, if desired). Lastly, the `Media` and `Video` controls had some API inconsistencies and gaps (i.e. several published events are never fired), so these samples access a few "internal" APIs to implement useful functionality; was not sure how strict to be about this.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>