CRM: generate a new reference on cloned events
testCRM: remove a duplicated test
CRM: Event.getPropertyDictFromContent should not lookup source/destination when defined on document
CRM: remove custom code that should not have been here
get rid of send_mail variable in new event workflow

We always generate the event upon start. User can pass another transition not to generate the event.
testCRM: small simplifications
Move Event_send logic of sending email in MailMessage_send.

We only want to send an email for mail message portal type
CRM: send all events (Compatibility warning below)

This rely on a change in erp5_base where Event_send does nothing and MailMessage_send sends email instead, otherwise mails will be sent for all started events.
Remove old duplicated implementation of sending email
update comments
CRM: test we send only one email
NotificationTool: use event workflow instead of calling low level send
NotificationTool: subject is required
fix from_url missing
Remove obsolete method on obsolete class

When MailMessage portal type is not installed, then temp mail messages will use
this class. The plan is still to remove the class, but for now just remove this
method that can overload Event.send
NotificationTool: import a temp constructor with same name as notifier portal type
Make Constant.PropertyGetter a new style class
little simplifications
Adjust Mail Message sending by activity