Add filestore data location for ir_attachment module

[enricostano]

https://github.com/odoo/odoo/blob/bd004ac75e2249fded10e69c7e1d3bf5b5f64911/odoo/addons/base/models/ir_attachment.py#L62

https://github.com/odoo/odoo/blob/12.0/odoo/tools/config.py#L122

By default Odoo will store files in /home/odoo/.local/Odoo.

[enricostano]

@cesarlr @danypr92 is this still valid?

[enricostano]

It's still valid, but not urgent.