Release 0.3.0

[schabdo]

Preconditions

• [x] Migrate to Vaadin 8 (https://github.com/eclipse/hawkbit/pull/980)
• [x] Bump Vaadin version to 8.11.x (https://github.com/eclipse/hawkbit/pull/1010)
• [x] Migrate to Spring Boot 2.3.x (https://github.com/eclipse/hawkbit/pull/1018)
• [x] EclipseLink version upgrade will brake SQLServer support (https://github.com/eclipse/hawkbit/issues/1045)

Release PRE steps

• [ ] Check for missing CQs
• [ ] Create project plan
• [ ] Request PMC approval
• [ ] Generate IP Log

Release

• [ ] Check that all CQs are completed
• [ ] Complete Release Review
• [ ] Technical Release 0.3.0 on Maven Central
• [ ] Update release notes and docker setup