Changes

Summary

1. Implement access and retrieval of message_reference (#1686) (commit: 969f3f3) (details)

Commit 969f3f399d050d5470ce27f2a78a8597914c39f9 by noreply Implement access and retrieval of message_reference (#1686) (commit: 969f3f3)
	src/main/java/net/dv8tion/jda/api/entities/MessageReference.java
	src/main/java/net/dv8tion/jda/internal/entities/SystemMessage.java (diff)
	src/main/java/net/dv8tion/jda/internal/entities/AbstractMessage.java (diff)
	src/main/java/net/dv8tion/jda/api/entities/Message.java (diff)
	src/main/java/net/dv8tion/jda/internal/entities/EntityBuilder.java (diff)
	src/main/java/net/dv8tion/jda/internal/entities/ReceivedMessage.java (diff)