Stunner - Allow the introduction of emails in Tasks notifications

Acceptance Criteria

• A new textbox field and label should be added in Notifications, just below "to user(s)", with the label "to email(s)". It should alow special characters allowed as email addresses and comma as separator
• After clicked on "Ok", the Notification screen should show the column "to email(s)", just after "to group(s)", with the content listed in the related row.
• In the marshaled file, should be added the new field "toemails" to the CDATA content:

  <![CDATA[[from:katy|tousers:john,katy|togroups:|toemails:someemailhere@redhat.com,anotheremail@redhat.com|replyTo:|subject:|body:]@[PT1M]]]></bpmn2:from>