* [presubmit] Enforce language attribute in projectt.yaml to be always set.
* Update documentation, better presubmit check, new project template.
* add docstring to templates.py
* Add example values in the project.yaml template and remove python value for now
* Add "project: c++" to 256 projects
* format
* Add labels and selective_unpack sections to the presubmit check
* fix incorrect auto_ccs format in three projects
* fix nss emails after rebase
[Example failure](https://oss-fuzz-build-logs.storage.googleapis.com/log-8eabbac0-bb8f-4f90-a840-f23efe427e0e.txt)
This only occurs on the fuzzers for some reason, not on Travis CI. Error is similar to https://github.com/bazelbuild/bazel/issues/5640.
Change spawn strategy to `sandboxed` to work around this. Not sure why it was `local` to begin with (other than a slight performance improvement).
Tested locally to ensure this spawn strategy will work.
```
python infra/helper.py build_fuzzers --sanitizer address --engine libfuzzer --architecture x86_64 esp-v2
```
Signed-off-by: Teju Nareddy <nareddyt@google.com>
Teju Nareddy