[FIX] stock: Never hide the invoice control on pickings

Invoice control field was invisible, and we cannot change value if none selected or copy picking in.
Fixes #3636
[FIX] fix editing one2many in some cases (web)

See issue #3964 for more detail.  Main problem was caused by commit
f0e331e005d8.  It set the key name+'__display' to false when reloading
a record for all field types, but it was only concerned with many2many.
[FIX] base_calendar: meetings email notification recipients

Reminder emails are generated based on the list of attendees.
The email_to field used to be a string with a list of emails separated by spaces
while the comma is the valid separator (RFC2822).
Fixes #3933 #3784 #2033
[MERGE] forward port of branch 7.0 up to 419d934