[8.0] Port the module 'account_move_template' to the new API

This PR contains the module ***account_move_template*** ported to the new API.
Test and installation seems to me ok.

Let's see what will be the TravisCI response and your reviews :wink: 
here `self` is a model and `_get_template_line(line_number)` should be called on a recordset. Maybe this method is also a `@api.multi`?