TEIIDDES-1750: Selection issue when deleting table object

* The DeleteWorker assigns the selected objects to the delete command
  during its execution phase. However, during the pre-run phase, the
  model editors associated with the selected objects are opened. If the
  'link with editor' option is selected then the focus on the editor
  causes the selection to change PRIOR to the execution phase.

* DeleteEObjectAction
 * Assigns the selected objects to the DeleteWorker at the start of the
   pre-run phase

* DeleteWorker
 * Caches the selected objects when the set method is called

* Convert multiple uses of arrays into lists
Creates an abstract extension registry

* Factors out the common functionality of the Teiid Runtime Registry into
  an abstract class that can be extended by similar registry implementations
TEIIDDES-1739: Refactors the DDL importer

* Separates out the ddl importer into specialised node sub-importers

* Node Importers keys against the parser id returned from modeshape

* spi plugin provides the node importer registry and extension point