SP-984 - Regression of PDI-11103 - Performance of Sort Rows step in 5.0 (5.0)

junit tests added
Conflicts:
	test/org/pentaho/di/TestUtilities.java
	test/org/pentaho/di/trans/steps/sort/SortRowsTest.java
SP-984 - Regression of PDI-11103 - Performance of Sort Rows step in 5.0 (5.0)

checkstyle applyed
SP-984 - Regression of PDI-11103 - Performance of Sort Rows step in 5.0 (5.0)

PDI-11103 - Performance of Sort Rows step in 5.0

refactor existing code, perfomance restored.
Conflicts:
	engine/src/org/pentaho/di/trans/steps/sort/SortRows.java
	engine/src/org/pentaho/di/trans/steps/sort/SortRowsData.java
Merge pull request #340 from prakapenka/SP-948

SP-984 - Regression of PDI-11103 - Performance of Sort Rows step in 5.0 (5.0)