MT#5879 Fix reseller relation for invoice tmpl

(cherry picked from commit a860b52c154f811acd907ca05592407b55263cfb)
MT#5879 Cleanup invoice tables and add gpp contact

Drop unnecessary invoice template tables.
Provide proper columns in invoice and invoice templates table.
Add general purpose columns to contacts.

(cherry picked from commit 9a255c41b5c888dedb9473f14209e3eb3b61eeb7)
MT#7377 Add is_pbx_pilot to prov subscriber

(cherry picked from commit 0167baa629680cabf72ed5e6540fa3bcc887ba3b)
MT#5879 Rework invoice-relevant tables.

(cherry picked from commit 85049c3ccc1fbebf62753151ed3b4634607b4b23)
MT#7471 Add contract preferences schema.

(cherry picked from commit 0f7460d61b75454c9d5dba526e6e32911762d52c)
MT#5789 Add invoice email template relationship into contracts.

(cherry picked from commit 20887f5dba5c2dc3dddf918518982ee258d0c33a)
MT#5879 Add sent marker into invoices and country_name into contacts.

Country_name as a method to wrap country code into full name.

(cherry picked from commit f5fca0819c3567e9b573c1697df993e45ea476e2)
MT#5879 Set invoices data column size to 16M.

(cherry picked from commit 041207b98f4e28e4d2fa74415f8a7ae63ab38e17)
MT#5879 Remove country_name wrapper.

(cherry picked from commit 5a1a07811bfdbb5e21794bdfdf5e0fefeb002c68)