Allow new ticket without required contact fields

If a staff member creates a new ticket and cancels the user-lookup /
create-new-user dialog, and the contact information form has a required field
other than the name and email address fields, the ticket cannot be created
because the required fields for new clients are not shown and can therefore
not have a required value.

This patch allows new clients to be created without the required fields when
the ticket is created by staff members.
Hide signature box when empty

Also, default size should not decrease if different signatures are selected
pdf: Ensure a paper size is set
Merge pull request #656 from greezybacon/issue/ticket-by-staff-fails

Allow new ticket without required contact fields

Reviewed-By: Peter Rotich <peter@osticket.com>
forms: Better failsafe for __toString

This mostly helps when fields change types. If the type of the field
currently cannot convert previous data to a string (like if a short-answer
field was changed to choices), the textual representation of the PHP value
of the field data is given.
Merge pull request #659 from greezybacon/issue/652

forms: Better failsafe for __toString

Reviewed-By: Peter Rotich <peter@osticket.com>
Merge remote branch 'upstream/develop-next' into develop-next
Merge remote branch 'upstream/develop' into develop-next

Conflicts:
	include/class.ticket.php