[DMN Designer] Properties panel drill down to DMN component level

The Properties Panel currently shows properties for Stunner-level "graph" components.

We need, for DMN, the Properties Panel to show the properties of DMN elements' properties at the "grid" level. For example, when a Context is selected the Properties Panel should show only the top level properties for the Context (i.e. not those of its ContextEntries). Selection of a ContextEntry should refresh the Properties Panel to show only the top-level properties of the ContextEntry. Selection of the ContextEntry's Expression should again refresh the Properties Panel to show only the top-level properties of the Expression and so forth.

Properties on the Grid Level

The selection on the grid level should show the properties below. Please notice that selection of multiple cells, rows or columns should show empty properties panel.

(everything should have ID, Description properties. Components which inherit from "NamedElement" should also have Name property)