Add .gitignore and .ratignore files for various directories

doc/licenses/retrofit-2.11.0/NOTICE

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+Copyright 2013 Square, Inc.
+
+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.

doc/licenses/retrofit-2.11.0/README

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+Retrofit (https://square.github.io/retrofit/)
+---------------------------------------------
+
+    Version: 2.11.0
+    From: 'Square Inc'
+    License(s):
+        Apache 2.0
+

doc/licenses/retrofit-2.11.0/dep-coordinates.txt

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+com.squareup.retrofit2:retrofit:jar:2.11.0
+com.squareup.retrofit2:converter-jackson:jar:2.11.0