[FIX] website_forum: added a forgotten required on post_type on the post model. Indeed a post is a question, a link or a discussion and cannot be something else.
[FIX] website_forum: added a forgotten required on post_type on the
post model. Indeed a post is a question, a link or a discussion and cannot be
something else.

Added constraints to avoid having posts that do not match the accepted types
on the forum; and to avoid having forums having a default post type not
matching the accepted ones.

syci/OCB,laslabs/odoo,laslabs/odoo,microcom/odoo,ygol/odoo,alhashash/odoo,alhashash/odoo,laslabs/odoo,optima-ict/odoo,hip-odoo/odoo,hip-odoo/odoo,dfang/odoo,addition-it-solutions/project-all,laslabs/odoo,addition-it-solutions/project-all,alhashash/odoo,tvtsoft/odoo8,laslabs/odoo,Grirrane/odoo,microcom/odoo,mkieszek/odoo,storm-computers/odoo,dfang/odoo,storm-computers/odoo,sysadminmatmoz/OCB,addition-it-solutions/project-all,bplancher/odoo,mkieszek/odoo,ygol/odoo,bplancher/odoo,hip-odoo/odoo,stephen144/odoo,alhashash/odoo,syci/OCB,ygol/odoo,Grirrane/odoo,sysadminmatmoz/OCB,syci/OCB,dfang/odoo,storm-computers/odoo,Elico-Corp/odoo_OCB,Elico-Corp/odoo_OCB,tvtsoft/odoo8,mkieszek/odoo,stephen144/odoo,Elico-Corp/odoo_OCB,Elico-Corp/odoo_OCB,optima-ict/odoo,bplancher/odoo,Elico-Corp/odoo_OCB,sysadminmatmoz/OCB,storm-computers/odoo,hip-odoo/odoo,tvtsoft/odoo8,syci/OCB,microcom/odoo,addition-it-solutions/project-all,ygol/odoo,tvtsoft/odoo8,tvtsoft/odoo8,addition-it-solutions/project-all,mkieszek/odoo,microcom/odoo,tvtsoft/odoo8,syci/OCB,microcom/odoo,sysadminmatmoz/OCB,hip-odoo/odoo,storm-computers/odoo,stephen144/odoo,Elico-Corp/odoo_OCB,dfang/odoo,optima-ict/odoo,bplancher/odoo,Grirrane/odoo,bplancher/odoo,bplancher/odoo,dfang/odoo,stephen144/odoo,Grirrane/odoo,ygol/odoo,ygol/odoo,stephen144/odoo,mkieszek/odoo,alhashash/odoo,addition-it-solutions/project-all,syci/OCB,ygol/odoo,storm-computers/odoo,sysadminmatmoz/OCB,sysadminmatmoz/OCB,laslabs/odoo,alhashash/odoo,microcom/odoo,optima-ict/odoo,stephen144/odoo,sysadminmatmoz/OCB,optima-ict/odoo,optima-ict/odoo,dfang/odoo,Grirrane/odoo,mkieszek/odoo,hip-odoo/odoo,Grirrane/odoo