add examples for snmpv2 with a different community, and snmpv3

Index: generator/generator.yml
--- generator/generator.yml.orig
+++ generator/generator.yml
@@ -4,6 +4,17 @@ auths:
     version: 1
   public_v2:
     version: 2
+  somecommunity_v2:
+    version: 2
+    community: some_community
+  authpriv_v3:
+    username: some_user
+    security_level: authPriv
+    password: some_authkey
+    auth_protocol: SHA
+    priv_protocol: AES
+    priv_password: some_privkey
+    #context_name: context
 
 modules:
   # SNMPv2-MIB for things like sysDescr, sysUpTime, etc.
