Using a new method to push pages to the PageStack and clickable HeaderBar labels and icon

The current pageStack mechanism is to push any page regardless of what is already on it. Among other issues this was causing some critical errors with pushing pages directly from the headerBar and also there is no specific mechanism yet to highlight the current root page on the global drawer which with the new mechanism is expected to be fixed.
By adding a function to control the page pushing behavior, I have added support to push only the pages that need to be there.

Example:
To have the EntryPage on top of the stack, we would probably want to push only the
FeedListPage -> EntryListPage -> EntryPage
This is a much more optimized way of pushing pages onto the stack as it allows total control over what the application is supposed to display. We need to be careful with the order of pages that are to be pushed.