Fork/master fix pipeline

[wildone]

Which problem is this PR solving?

This has been mentioned in #197 and various other issues.

Short description of the changes

This updated the pipelines and related scripts to build and release plugin for nginx into the release assets.

I've updated the Ubuntu pipeline to create a new automated release with the plugin asset. The pipelined creates a new release using the git describe so it will always create a new release when commits happen into master.

Also included:

• added automatic release notes based on commit messages.
• ability so [skip ci] - don't run pipelines.
• ability to [ci ubuntu] - run only ubuntu pipeline

[AppVeyorBot]

:x: Build jaeger-client-cpp 222 failed (commit https://github.com/jaegertracing/jaeger-client-cpp/commit/a92259055e by @wildone)

[AppVeyorBot]

:x: Build jaeger-client-cpp 223 failed (commit https://github.com/jaegertracing/jaeger-client-cpp/commit/6ba26e8f54 by @wildone)