Add an optional back link to the navbar
Add an optional back link to the navbar

https://trello.com/c/icPE8Z6a/34-user-sbat-to-view-monthly-summary

This is required to come back to the leaderboard from the monthly
summary page.

- Send a boolean prop to the navbar to show / not show the back link
- Pop the latest route on tap of the back link

multunus/moveit-mobile,multunus/moveit-mobile,multunus/moveit-mobile