Update to latest version of qtsingleapplication for Qt5 support

Signed-off-by: Taylor Braun-Jones <taylor.braun-jones@ge.com>
Added qtsingleapplication customizations again on top of updated files.
Use Qt5 QTemporaryDir class instead of custom Qt4 code.
Merge branch 'bug-17529-Upgrade-qtsingleapplication'

* bug-17529-Upgrade-qtsingleapplication:
  Use Qt5 QTemporaryDir class instead of custom Qt4 code.
  Added qtsingleapplication customizations again on top of updated files.
  Update to latest version of qtsingleapplication for Qt5 support