Navigation and HomePage changes

1. Master page (MainPage) that contains a header text which shows type
of page selected currently. Default is Home. It also contains a Frame
whose content switches.
2. HomePage added that contains list of all the Estimate XMLS in Local
directory. On selection of a list item, details are shown in detail
section in the right of the list view.
3. All the other pages (Empty right now)- HomePage, DefinePage,
ConfigurePage, EstimatePage, ReviewPage, CopyPastePage.
4. Bottom app bar added that appears on right click. Bottom App bar
contains buttons – Home, Define, Configure, Estimate, Review,
Copy/Paste.
5. Content of the frame changes according to currently clicked button.
Ex Click Configure and ConfigurePage will be loaded.
@Ujwal – Please move your Define page changes to DefinePage.xaml.
6. ViewModelBase, MainPageViewModel and HomePageViewModel added.
7. Few converters/helpers/enums added.