Added epg history configuration (bug 33943).
Added background of message format doc.
Synchronous messages described.
small changes
Added messages examples.
Removed description of messages (it is in release-3.0.0).
Documentation for delete content call (Bug 35675).
bug 38460 - fixed typo
Merge branch 'release-2.4.0' into release-2.4.1
Merge branch 'release-2.4.1' into release-3.0.0

Conflicts:
	eda/messaging.rst