Introduces automated GH actions build and plugin release automation

This switches the plugin to similar build+release process as other plugins, via GitHub Actions.

- Uses gocd-plugin-gradle-task-helpers to generate plugin metadata
- Automatically generates changelogs
- Automatically bumps versions by including a build/commit number
- Minor bumps to libraries
- Removes need for commons-io to reduce plugin size

Author: chadlwilson

.build/docker-ops

@@ -1,11 +1,3 @@
-
-If you are submitting a new feature then please do a **minor version bump** by
-```
-./tasks.sh set_version 0.X.0
-```
-
-If you are submitting a fix, then do not change any versions as patch bump is made right after each release.
-
 PR should contain:
  - tests of new/changed behavior
  - documentation if adding new feature