several UI fix and bug fix#19

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guoyk93 wants to merge 3 commits intosubdigital:masterfrom

guoyk93:fix_iOS7

Commits on Feb 20, 2014

backDropView opacity 0.8 is too thick, change to 0.4
yankeguo
committed
make picker background color white ; default for iOS 7 is translucency
yankeguo
committed
logic fix for the situation when initial index is setted before present
yankeguo
committed