add a shell script for cleaning up all kinds of build artifacts

* it cleans up all 'bin' and 'obj' directories, as well as .vs etc
* can help to fix build problems and return to a clean initial state
* should work on Mac, Linux, WSL, ...

Author: janusw

cleanup.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+# remove 'bin' and 'obj' directories
+find . -type d \( -name 'bin' -o -name 'obj' \) -prune -exec rm -rf {} \;
+
+rm -rf Source/packages/
+rm -rf Source/.vs/