Fixes error in TeiidServer isConnected logic

* Needs to separately test for the admin field being null since otherwise
  an NPE is still possible.
TEIIDDES-1622: Move the checkReadOnlyResource method

* Migrate the funtion to RefactorResourceUtils so that other refactoring
  objects can make use of it.
WIP for refactoring of delete eobjects action
TEIIDDES-1612: Refactor the calculateRelatedChanges method

* Finding related resources and vdb files is the same for each refactoring
  except what it actually done with them so delegate to the utilities
  class and introduce callbacks to perform the specific functionality.