[REF] Chatter: refactored system for read more / read less, now based on html_email_clean instead of the expander library.
[IMP] Chatter: first message is truncated after 100 characters, other messages after 300 characters; cleaned code about expan management.
[MERGE] Sync with trunk
[MERGE] Sync with trunk
[FIX] mail: fixed merge issue, forgottent conflict
[MERGE] Sync with trunk
[MERGE] [IMP] mail: Chatter: better read more / read less in messages, using the improved html_email_clean.

[REM] mail: removed jquery.expander library as there is no need anymore of this external lib