Ignore out directory everywhere

After IDEA-175172 JPS does not use Gradle's output directories
when buildsing imported projects.
Now JPS uses an `out/` directory instead,
which wasn't gitignored anywhere besides the project's root.

.gitignore

@@ -7,7 +7,7 @@
 /gh-pages
 /ideaSDK
 /android-studio/sdk
-/out
+out/
 /tmp
 workspace.xml
 *.versionsBackup