Resiliency test: add documentation.

slapos/resiliencytest/README.txt

+This module is supposed to be launched from the "test" instance of a resilient
+service (usually deployed using "test" software type).
+
+One entry point, if the service has been deployed
+from a "scalability" test node, so with special parameters, will automatically
+communicate to an ERP5 TestNode Master, and start the test.
+
+The other entry point is supposed to be run manually from a simple "test"
+instance without special parameter, and will manually run the test.
+
+
+
+This module contains:
+ * The code to start the test from a testnode / manually
+ * A Resiliency Test Suite framework (in suites/), used to easily write new
+   test suites
+ * A list of test suites