Add codecov.io coverage collection from AppVeyor

Also had to add new project to redirect CTest output, add
separate batch scripts for AppVeyor because it doesn't handle
multi-line batch scripts in yaml properly, and other helper
scripts.

misc/appveyorMergeCoverageScript.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python2
+
+import glob
+import subprocess
+
+if __name__ == '__main__':
+    cov_files = list(glob.glob('cov-report*.bin'))
+    base_cmd = ['OpenCppCoverage', '--quiet', '--export_type=cobertura:cobertura.xml'] + ['--input_coverage={}'.format(f) for f in cov_files]
+    subprocess.call(base_cmd)