Rename std.env() to std.extVar() (breaks compatability)
Add std.flattenArrays and std.manifestIni
Improve and document multi capability
Improve error message
Add some more stdlib functions
Fix stacktrace line numbers in test goldens
Update javascript build
Hidden field semantics: now inherit by default
Build jsonnet with bazel and BUILD files.

Details:
- Breaks Makefile. Sad trombone.
- Add bazel-* directories to .gitignore.
- Add WORKSPACE to designate bazel workspace root.
- Move source files into a subdirectory of the workspace root.
- Add tools/... directory that bazel needs to actually build anything.
  This part of the change copied nearly unmodified from
  https://github.com/google/bazel/tree/master/example_workspace.
Move test stuff from //test_suite to //src/testdata.
Merge branch 'build-with-bazel' of github.com:cdrichards/jsonnet into build-with-bazel