* add new bash script for release version update
* update version using the bash script
* Fix shippable build
Modify `artifactId` of `CI/pom.xml.shippable` to be `openapi-generator-shippable-pom`
* Comment ensure-up-to-date
* add shippable to the release script
* Updates README based on new release changes (#271)
The release management changes moved from maven-publish (newer plugin)
to maven (older plugin, only one that works currently with signing).
This updates docs in the samples/local-spec project with current
directions.
Also:
* Includes sonatype releases/snapshots on repo lookup
* Adds openApiGeneratorVersion property
