* Exporter/OCAgent: Add OcAgentNodeUtils.

Add utilities for detecting and creating Node.
Equivalent to
https://github.com/census-ecosystem/opencensus-go-exporter-ocagent/blob/master/nodeinfo.go.

* Fix nullness checker.

* Use a local VERSION string in OC-Agent Exporter.

Remove unsafe way to give permissions.

* Contrib: Add opencensus-contrib-opencensus-proto-util.

* Update CHANGELOG.

This commit also sets the version of the com.google.guava:guava-jdk5 artifact in
the generate_workspace command and removes the
com_fasterxml_jackson_core_jackson_core dependency from BUILD.bazel.

Some directory names were changed, so the list of readmes in RELEASING.md needed
to be updated.

Now protected branches can be specified with a pattern, so we can protect all
release branches with one rule. See
https://help.github.com/articles/about-protected-branches/.  There is no need to
enable branch protection when making a release.

* Initial import of OpenCensus/Sleuth integration.

* Minor fixes for integration with master.

* Adds a README.

* Removes hardcoded dependencies in build file.

* Adds contrib to spring_sleuth file path.

* Updates package names appropriately based on file renames.

* Fixes build paths.

* Fixes for build checks.

* Mark as experimental.

* Minor fixes for build files (space vs tab).

* Minor fixes for build files (space vs tab).

* Update README to absolve Spring Sleuth team of any responsibility for this spring_sleuth plugin.

* Minor fixes for import control (space vs tab).

* Tag public classes @since 0.16

* Adds javadoc for public methods not already documented.

* Updates OpenCensusSleuthTracer to pass nullness checks.

* Fixes for formatting issues.

* Fixes for typos.

* Suppresses the check return value warning added by gRPC.

* Suppresses the check return value warning added by gRPC.