Merge pull request #4 from benlau/segmentedcontrol

Added new component Segmentedcontrol - An implementation of UISegmentedControl
NavgiationStack.qml : Extra condition checking on push()
NavigationStack.qml : Fixed the problem that pushed() signal is not emitted for push()
Fix the broken test case
Merge pull request #5 from benlau/refactor-navigation-view

Refactor NavigationView and added new component