[IMP] crm : usabilitu improvements (default filters, load to opp wizard)

...le converting leadtoopportunity,Improved leadtoopportunity wizard,Hide Mark-As-Lost in lead, mail : Improved mail compose wizard
hello,
the purpose of this code is,to add contact name through opportunity wizard if user forget to add in leadtoopportunity form view.
the reason for manipulating contexts is,if user forget to enter contact name in leadtoopprtunity form  then contact name can add through wizard.
it is requested from this task, https://pad.odoo.com/p/r.OJUwKfbQkM1ONtOj