Provide AirVantage OAuth implementation

Implementation to use the OAuth2 service from https://airvantage.net.

Change-Id: Ie992a958abc3dc925c04e29d2a9827878e51e1cd
diff --git a/.gitignore b/.gitignore
index 898d584..2338df2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,4 @@
 /bazel-out
 /bazel-testlogs
 /.idea
+*.swp