[15.0][ADD] sale_product_matrix_secondary_unit: New module

[chienandalu]

With this module we'll be able to set the secondary units in the product
matrix for a quick quotation for those products using this kind of
configurator.

cc @Tecnativa TT52531

please take a look @sergio-teruel @CarlosRoca13 @pedrobaeza

[CarlosRoca13]

In runboat i got this error when opening the matrix:

Error: QWeb2 - template['product_matrix.matrix']: No enumerator given to foreach
    at Object.exception (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_common.js:57861:19) (/web/static/lib/qweb/qweb2.js:48)
    at Object.foreach (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_common.js:58023:22) (/web/static/lib/qweb/qweb2.js:210)
    at Engine.eval (eval at _render (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_common.js:58285:33), <anonymous>:19:23) (/web/static/lib/qweb/qweb2.js:472)
    at Engine._render (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_common.js:58274:58) (/web/static/lib/qweb/qweb2.js:461)
    at Engine.render (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_common.js:58266:26) (/web/static/lib/qweb/qweb2.js:453)
    at Engine._render (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_common.js:58296:29) (/web/static/lib/qweb/qweb2.js:483)
    at Engine.render (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_common.js:58266:26) (/web/static/lib/qweb/qweb2.js:453)
    at Class._openMatrixConfigurator (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_backend.js:153961:30) (/sale_product_matrix_secondary_unit/static/src/js/section_and_note_widget.js:61)
    at onSuccess (http://oca-product-attribute-15-0-pr1854-7ca9f9ba4811.runboat.odoo-community.org/web/assets/debug/web.assets_backend.js:151529:22) (/product_matrix/static/src/js/section_and_note_widget.js:78)

[sergio-teruel]

Hi..
The name on secondary is not shown correctly, the used field seems name instead of display_name

In matrix view

Some errors are shown when I mix different secondary units on same sale order

We can define different seconday units by variant, This is not covered, is it?