Initial commit of FeedBoard project

Consist of 3 components, namely main app (FeedBoard), data-library, and
background-agent (ScheduledTaskAgent1)
Committed image assets
Added homepage (major functionalities are not completed at this point)
Implemented search bar
Implemented bottom app bar
Added taps' events in NewsItemPage
Achieved run flow from home-page to news-header-page
Modified preload in category-page to make page transition smoother
Fixed search
Read categories' setting from json file; Worked on add-to-homescreen
Added data-retrieval helper
Enhanced add-to-homescreeen by news-item (pin-type) from the rest
Configured to retrieve data from isolated-storage and through instant-fetching conditionally