Cleanup the helper scripts

* Remove from __future__ import print_function, because we
  no longer support Python2.
* Clean out unused parts of tools/scripts/scriptCommon.py
* Move appveyorMergeCoverageScript to Python3
* Update user reporting in *release scripts
* Cleanup module imports

tools/misc/appveyorMergeCoverageScript.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 
 import glob
 import subprocess