Feature request: allow parents from more than 1 level in select dynamic cascade

[Giuse69]

In every stage of a Select Dynamic Cascade, just one single value from previous field in the cascade can be used for the query ([parent]), while the query sometimes needs also previous parents.
Example:

1. select a type of product from a product_types table
2. select a brand that sells the type of products selected in stage1 (parent = type of product) from a product_brands table where each row is a brand and holds an array with types of products made by that brand
3. select a product of the brand selected in stage 2 (parent = brand) AND of the type of products selected in stage 1 from a product tables with columns {id, name, product_type, brand}. PROBLEM: selected product type from step 1 is not accessible in the query since it is two steps before.

Proposal: transform [parent] from a single value to an array and in each step of the cascade current field adds its parent to the array. In this way in any step/field of the cascade it is possible to access selected choice in every other step.