* added bug report and feature request issue tempaltes
* copied pull_request_template.md to .github folder
* Updated the DateCalculation narrator logic to use PropertyChangedCallbacks for the DateResultLabel and DateDiffAllUnitsResultLabel TextBlocks.
* Reverted textblock callback changes and added an event handler for when the radio buttons are checked.
* Revert NarratorAnnouncement.h changes and removed unused code from DataCalculator.xaml.h. Updated comments in RaiseNotification method in DateCalculator.xaml.cpp
* Reverted changes in NarratorAnnouncement.h and NarratorAnnouncement.cpp
* Added SAL annotation to AddSubtractOption_Checked
* Remove namespaces from input types on AddSubtractOption_Checked