Add bazel standalone build

Test plan:
- bazel clean --expunge
- bazel build uploadvalidator
- bazel test --nocache_test_results //...
- Deploy plugin to gerrit site
- Verify plugin loads without errors
- Verify plugin functionality
- Run tools/eclipse/project.sh
- Import project in Eclipse and verify classpath contains all
  dependencies

Change-Id: I3743c07bed664737743fc5020ef3853f5b46358f
diff --git a/.gitignore b/.gitignore
index 80d6257..52a5343 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,8 @@
-/target
 /.classpath
+/.primary_build_tool
 /.project
 /.settings/org.maven.ide.eclipse.prefs
 /.settings/org.eclipse.m2e.core.prefs
+/bazel-*
+/eclipse-out
+/target