added light theme navbar text-shadow

Issue
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The win8 theme for navbar had black text-shadow, when switched to light theme it changed the text also to black, this made the navbar items with black text with black shadow. 

Test Case
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Open the kitchen sink app, change to win8 theme and then change to lighter theme. Notice that the nav bar items have black text/icon with black shadow, making it it look blurry

Fix
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added css for light navbar with white text-shadow