[FIX] base: allow server actions to en/decode base64
[FIX] base: allow server actions to en/decode base64

This is usefull when dealing with binary fields.
This was possible in previous versions in python 2 using
`str.encode('base64')`.

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo