ANG-2680: Allow for multiple, consecutive spaces in MarqueeItem.

Issue
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Multiple, consecutive spaces are collapsed into one space in a number of controls, including the caption of a `GridListImageItem` and the title of a `VideoPlayer`.

Fix
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We make a general fix for all `MarqueeItem` controls and set the `white-space` property value to `pre`. I went through all the `Moonstone` samples and didn't notice any side effects from this modification.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>