MT#5879 Create default invoice email template.

Allow null reseller_id for very default email templates,
which will be used to create default reseller templates.

(cherry picked from commit f2676815c06128cc435ab761e5787270aa18f6c2)
MT#5879 Fix forgotten subject field for default invoice email template.

(cherry picked from commit 1fa7b70b01c53d1af98b6d4eb844bcac624936e5)
MT#7377 Add is_pbx_pilot to prov subscriber

(cherry picked from commit f6b7153d8c3a49dd77fbb5d9c13c128ca1523607)
MT#5879 Rework invoice-relevant tables.

Move VAT fields from billing_profiles to contracts.
Drop unnecessary tables.
Cleanup invoice and invoice_templates table.

(cherry picked from commit b956910e76d5e43b89ef93d3978e784349dab7b0)
MT#5879 Rename bank_name to bankname.

(cherry picked from commit 345769986422611b199829eb397542b57cd296a9)
MT#7471 Add contract preferences schema.

(cherry picked from commit 3e11d5414fab4a9737fea70c3cf6f848e058d8e6)
MT#7471 Make ncos and block list contract prefs

(cherry picked from commit 70c48dc4ab2aac4c8a693174585d123276dad29b)
MT#5879 Set invoice data column to 16M size.

(cherry picked from commit 6edbf0dd3fe0c712eb54f27c4262e16b46575f03)
MT#5879 Add sent masrker to invoices.

(cherry picked from commit d3cb00546ef4a57321afb1f2113378a80e8cb325)
MT#5879 Set invoice data column to 16M size.

(cherry picked from commit 604ab9c559cdaf5d9fb3bebad87f607795adf5fb)
MT#5879 Change default invoice email template.

(cherry picked from commit 3d8a8fbf5545ac1ac982aea28177ac0d60934d9e)
MT#7471 Fix contract schema and add down script

(cherry picked from commit 806453a8b60341270ea31dadf1aef6ece21aa507)