[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: 
I fear to confuse you more with that: I spoke about "model" but in fact that's a recordset with no records.
When the method is decorated with `api.model`, usually `self` is a recordset with no records (so it sounds like it is the model itself to me, you can call ORM methods (search, create) on it but there are no records). When it is decorated with `api.multi` then it is a recordset with 1 to many records.

The point is that `self` will be a different instance for different calls, so you can't store something on it as it could have be done prior v8 because the models were instantiated once.