Changing QR String to represent constant.
Implementing cancel button on QR Scan.
Implementing cancel button on QR Scan. Resolve #73.
Merge branch 'bug/dismiss-QR-scan' of https://github.com/RITAccess/accessmath into bug/dismiss-QR-scan

dated upstream into a topic branch.
Merge pull request #75 from RITAccess/bug/dismiss-QR-scan

Implementing Cancel Button