ISPN-2789 - OutOfMemoryError in case if LuceneCacheLoader.loadAll() is called

  * The bug is fixed.
  * Tests are added for verifying the bug.
  * Many new tests are added testing lucene directory.
ISPN-2788 - NullPointerException appears in case passing null as an exclusion list to LuceneCacheLoader.loadAllKeys()

   * Another new test is added checking the acceptance of null as a set of exclusions;
   * The test was reproducing the bug - the fix is extended.