Tell git to ignore files generated for/by IntelliJ Idea IDE.

bazel.iml is generated by scripts/setup-intellij.sh and .idea is
generated by IntelliJ Idea IDE after you open bazel project on it.

`git status` stops showing these when ran.

--
Change-Id: I2adc4a32ffb20d174b45be2b53deb098b6ef7fd9
MOS_MIGRATED_REVID=93139152

.gitignore

@@ -8,6 +8,7 @@
 /.project
 /.classpath
 /.factorypath
+/.idea/
 /fromhost/
 /base_workspace/bazel-bin
 /base_workspace/bazel-genfiles
@@ -17,6 +18,7 @@
 /base_workspace/examples
 /base_workspace/tools
 /base_workspace/third_party
+/bazel.iml
 /tools/jdk/jdk
 /tools/jdk/ijar
 /tools/jdk/JavaBuilder_deploy.jar