Version 1.0.0-alpha.28.4 (hotfix)

Applies five hotfixes to version 1.0.0-alpha.28:

• Bugfix: ProtocolVersion.date should always be serialized.
• Bugfix: load classDiscriminator for unkown polymorphism at runtime.
• Fallback to normal polymorphic serialization for non-Json formats in UnknownPolymorphicSerializers.
• Make sure ParticipantGroupSnapshot can be serialized as BSON.
• Devices can now be optional, specified as an isOptional property on DeviceDescriptor. Now, only non-optional master devices need to be deployed. Only non-optional master devices need to be deployed. (cherry-picked from #323)

Multiplatform release accessible through Maven:
https://mvnrepository.com/artifact/dk.cachet.carp