1.3 M3

• #1497 - Upgrade to Spring 5.3.5.
• #1494 - Improve HAL Link deserialization.
• #1493 - Upgrade to JaCoCo 0.8.6.
• #1492 - Upgrade to Jackson 2.12.
• #1491 - Upgrade to Kotlin Coroutines 1.4.3.
• #1490 - Upgrade to Reactor 2020.0.5.
• #1489 - Release 1.3 M3.
• #1484 - Significant performance regression in WebHandler.
• #1483 - Add support for HAL-FORMS options element.
• #1482 - Properly find project version number for CI jobs.
• #1477 - DelegatingEntityLinks does not override linkForItermResource(Class<?>, Object).
• #1474 - Migrate to new Sonatype infrastructure.
• #1421 - Use JDK 15 for CI testing.