add template-configs, script to launch network

This is the set of scripts I've written for myself over the years to easily
configure and run Osmocom core networks on my lab computer. I hope this will be
useful to others as well.
diff --git a/README b/README
index 2b441db..d6ce60e 100644
--- a/README
+++ b/README
@@ -1,3 +1,12 @@
+=== WHAT IS THIS?
+
+* quickly build the entire Osmocom core network stack from source, with a
+  generated top-level makefile (see the rest of this README file below).
+
+* quickly configure, launch and tear down an entire Osmocom core network on
+  your box (see net/README).
+
+
 === Quick Start
 
 sudo apt install \