[16.0][IMP] x2many_2d_matrix: add support of Related fields

[arnaudlayec]

This PR adds the support of pseudo-relational fields type "Reference" to x2many_2d_matrix.
See Odoo's ORM documentation about Reference fields.

Quite similarly to Many2one fields, the Reference fields' value and text must be fetched specificially.
This PR simply extends JavaScript conditions to test if fields are Many2one to add another condition to test if fields are Reference. If checked, text and value are retrieve correctly.
Example:

if (fieldType === "many2one") {
      column.text = column.value[1];
      column.value = column.value[0];
} else if (fieldType === "reference") {
      column.text = column.value.displayName;
      column.value = column.value.resId;
}

[OCA-git-bot]

Hi @ChrisOForgeFlow,
some modules you are maintaining are being modified, check this out!