Generate schemas dynamically from pieces provided by each object class

This way we benefit from:
* knowing which attributes are used/required by each object class and
  subclass
* Having validation function definitions near the class going to use them

Change-Id: I8fd6773c51d19405a585977af4ed72cad2b21db1
diff --git a/src/osmo_gsm_tester/obj/epc_srs.py b/src/osmo_gsm_tester/obj/epc_srs.py
index ec9dc44..f859df0 100644
--- a/src/osmo_gsm_tester/obj/epc_srs.py
+++ b/src/osmo_gsm_tester/obj/epc_srs.py
@@ -21,8 +21,15 @@
 import pprint
 
 from ..core import log, util, config, template, process, remote
+from ..core import schema
 from . import epc
 
+def on_register_schemas():
+    config_schema = {
+        'enable_pcap': schema.BOOL_STR,
+        }
+    schema.register_config_schema('epc', config_schema)
+
 class srsEPC(epc.EPC):
 
     REMOTE_DIR = '/osmo-gsm-tester-srsepc'