Bug #5329 : adding a new rules around WYSIWYG attachment management.
When updating a WYSIWYG attachment for a language with an empty content, the content for language is not saved but deleted. After that, if no content for any language exists for the attachment, then it is deleted from the JCR.
(adding some unit tests around the WYSIWYG controller)
(adding a List Object for SimpleDocument to centralize common behaviors)
Empty WYSIWYG documents are considered as non existing on display.
Merge branch 'bug-5329' into core-5.14.x
Bug #5553 : fixing the user session that can potentially never expire.
When the session of a user is becoming soon expired, a warning POPUP message is displayed to the user. But the display of this POPUP induced resetting of the user session time counters, and as a consequence, the user session was never ended !
Merge branch 'bug-5553' into core-5.14.x
Bug #5479 : JCR copy and move problems
Taking into account a new detected problem around the copy of a versioned attachment that had several language contents before to be turned into versioned attachment.
The problem was that the result copy of this kind of attachment was keeping only one of the several language contents for its initial version.

Conflicts:
	lib-core/src/main/java/org/silverpeas/attachment/repository/DocumentRepository.java