[ADD] Manufacturing: MO costs

[hojo-odoo]

This PR adds a new doc detailing how to track the costs of manufacturing orders.

[robodoo]

[hojo-odoo]

Hey @larm-odoo,

This is ready for the first round of review.

Thanks, John

[hojo-odoo]

Hey @ksc-odoo,

This doc is ready for final review.

Thanks, John

[hojo-odoo]

Hey @samueljlieber,

This doc is ready for technical review.

Thanks, John

[samueljlieber]

..... @robodoo delegate=hojo-odoo

[hojo-odoo]

@robodoo r+