Create a nom_build wrapper script (#508)

* Create a nom_build wrapper script

nom_build is a wrapper around ./gradlew.  It's purpose is to help us
deal with properties.  The main problem that it is trying to solve is
that when properties are specified using -P, we don't get an error if
the property we specify isn't correct.  As a result, a user or a build
agent can launch a build with unintended parameters.

nom_build consolidates all of the properties that we define into a
python script where the properties are translated to flags (actual
gradlew flags are also proxied).  It also generates the property file
and warns the user if the current properties file is out of sync with
the script and includes documentation on each of the properties.

gradle.properties

@@ -1,3 +1,12 @@
+# This file defines properties used by the gradle build.  It must be kept in
+# sync with config/nom_build.py.
+#
+# To regenerate, run config/nom_build.py --generate-gradle-properties
+#
+# To view property descriptions (which are command line flags for
+# nom_build), run config/nom_build.py --help.
+#
+# DO NOT EDIT THIS FILE BY HAND
 org.gradle.jvmargs=-Xmx1024m
 mavenUrl=
 pluginsUrl=
@@ -8,25 +17,12 @@ verboseTestOutput=false
 flowDocsFile=
 enableDependencyLocking=true
 enableCrossReferencing=false
-
-# Comma separated list of test patterns, if specified run only these.
 testFilter=
-
-# GAE Environment for deployment and staging.
 environment=
-
-# Cloud SQL properties
-
-# A registry environment name (e.g., 'alpha') or a host[:port] string
 dbServer=
 dbName=postgres
 dbUser=
 dbPassword=
-
-# Maven repository that hosts the Cloud SQL schema jar and the registry
-# server test jars. Such jars are needed for server/schema integration tests.
-# Please refer to <a href="./integration/README.md">integration project</a>
-# for more information.
 publish_repo=
 schema_version=
 nomulus_version=