RefObjects do not capture the link information on FromRevit converts

#### Description:

Currently `refObjects` on `FromRevit` converts use `ElementId` as key. This is not enough in case of linked models: in the extreme situation there could be objects of same time in two models, resulting in incorrect object being returned for one of them.

**Important:** `CachePanelGeometry` will require similar rework too, also material graded elements.