[13.0][MIG] ebill_paynet

[TDu]

This is based on #499 for 12.0 that has not been merged

• [x] account_invoice_export OCA/edi#212
• [x] base_ebill_payment_contract OCA/edi#207

[sebalix]

This depends on some other modules, maybe add that in oca_dependencies.txt to get tests running on Travis?

• account_invoice_export https://github.com/OCA/edi/pull/212
• base_ebill_payment_contract https://github.com/OCA/edi/pull/207

[TDu]

I open a new PR https://github.com/OCA/l10n-switzerland/pull/585 see why in the description. Thanks for all your reviews.

[TDu]

Replaced by #585 and #586. All comments have been taken care of.