Add initial implementation of YAML config file

This implements the basic framework that allows global YAML
configuration, per-environment custom configuration, and unit-
test-specific configuration.

TESTED=I deployed to alpha, ran some EPP commands through the
nomulus tool, and verified no errors.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=145422680

java/google/registry/env/local/backend/WEB-INF/appengine-web.xml

@@ -12,6 +12,10 @@
     <idle-timeout>10m</idle-timeout>
   </basic-scaling>
 
+  <resource-files>
+    <include path="/WEB-INF/*.yaml"/>
+  </resource-files>
+
   <system-properties>
     <property name="java.util.logging.config.file"
               value="WEB-INF/logging.properties"/>