[ADD] res_partner_fiscal_position

From https://code.launchpad.net/~lfreeke/therp-addons/7.0-res_partner_fiscal_position/+merge/235155 by @NL66278 and @lfreeke

@StefanRijnhart 
>Thanks! Looks really useful. Some comments:
>
>If I understand correctly, name_get() was modified to display the company of the fiscal position, because in a >superior company the fiscal positions of the underlying companies are accessible. This could help the user >not to pick a fiscal position of any other company than the one it is working for at that moment, but it does >not prevent a mixup of company data. I would prefer to filter the fiscal positions on the current user's >company. You may have to create a function field on res.country to be able to access this piece of data >though.
>
>In the manifest, please explain what is different in this module from the module that it is based on.
>
>The object instantiation in line number 150 is not needed in recent versions of Odoo and should be >removed.
>
>Please remove commented code in ll.136,137