Add run-tests to run all unit tests

We need to run it from the correct folder containing pytest.ini in
case the tests need certain indico plugins.

run-tests.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+for dir in $(find -name pytest.ini -exec dirname {} +); do
+    pushd "$dir" >/dev/null
+    py.test "$@"
+    popd >/dev/null
+done