Move build setup outside the main build gradle file.

This CL moves build processing logic into buildSrc file and
behind methods. This allows creating sub projects that can
use the same build file but only import a subset of support
library.

This CL does not decrease the complexity much. It just moves it
outside the main gradle file into more logical files as an
intermediate step to cleanup the build.

Test: same output before and after
Bug : -
Change-Id: I29d136ca866cc03c20c18f8d0b33e0152b320671
diff --git a/buildSrc/dependencies.gradle b/buildSrc/dependencies.gradle
index ba08b5f..92eaf51 100644
--- a/buildSrc/dependencies.gradle
+++ b/buildSrc/dependencies.gradle
@@ -1,3 +1,18 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 // Add ext.libs for library versions
 def libs = [:]