Activation.getObjectsDeep() should include "exists" elements too

Give them a finger and they'll want a hand. Give them a hand and they'll want an arm. (dutch proverb)

The Activation.getObjectDeeps() method introduced for DROOLS-1470 that also includes the accumulates elements, should also include the exists elements. For example:

  when
    $c : Computer(id = "c1")
    exists Process(computer == $c)
  then ...

with this data

  Computer c1;
  Computer c2;
  Computer c3;
  Process pA = new Process(c1);
  Process pB = new Process(c2);
  Process pC = new Process(c1);
  Process pD = new Process(c3);

gives this result

  activation.getObjectsDeep() // includes c1, pA and pC.

The goal is to identify all objects that matched when this rule got fired. In a negative score rule, all those objects are to blame and by focusing to change any of those, it's more likely to improve the overall solution.