[FIX] website_quote : usability fixes and improvements

1). Crash while selecting quotation template(template has products added) without selecting customer in quotation form.
Steps:
-> Install website_quote
-> Create one template with 1 or more products
-> Now create one sale quotation, do not select partner and directly select the quote template, you will face the error
solution => fix the SO, use a default pricelist and when the partner is setted it updates order lines prices. (whatever you use a tempalte or directly order line)

2). Validity Date should be invisible if quotation template is not selected, Validity date should be readonly mode after confirming the quotation, Suggested products should be in readonly mode after confirming the sale order

[Task] :  https://openerp.my.openerp.com/web#id=8409&view_type=form&model=project.task&action=327
[Pad] : https://pad.odoo.com/p/r.cnx1JRFvBi024Zyn
Those lines are quite complex to read... Avoid defining variables that you use only one. Try to clean a bit this code ! By the way context = dict(context=context, partner_id=partner_id) will create a dict containing a context dict. I do not think it is what you want to do.