-- Added MongoDB dependency, WIP.
-- Changed collection from List to ObservableCollection.
-- Added a few required fields in the Event class.
-- Some re-factoring and proper use of "var"s throughout the Manager(s) code
-- Added new exceptions inside Manager classes to handle failure during Push
-- Added filtered pulling: from a certain date, to a certain date. WIP.
-- Added first stub of database management
-- Added new required field inside Calendar.cs
-- Replaced DataStore usage with MongoDB.