Merge tag 'v3.19.1-1' into develop

Upgrade to Nexus 3.19.1

- Changed Nexus version from 3.18.1 to 3.19.1
- Changed Java version in Dockerfile to 8u222-1

- Added docker health check
- Add a start-up check whether the minimum number of CPU cores is reached (#36)
   - Starting with [Nexus Repository Manager 3.17](https://issues.sonatype.org/secure/ReleaseNote.jspa?projectId=10001&version=17890) a minimum number of 4 CPU cores is enforced, otherwise the Repository Manager is no longer guaranteed to work.
   - The added check adds a new healthy state during the Dogu start-up in order to provide a better visibility of the originating problem.
   - You can check for the health with the CES command `cesapp healthy nexus`

CHANGELOG.md

@@ -4,11 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
-
+## [3.19.1-1] - 2019-12-09
 ### Changed
-- Changed version from 3.18.1 to 3.19.1
-- Changed java version in Dockerfile to 8u222-1
+- Changed Nexus version from 3.18.1 to 3.19.1
+- Changed Java version in Dockerfile to 8u222-1
 
 ### Added
 - Added docker health check