Add method to get max row count

It count max row count with data and exclude last row. It is a must that
excel documents contains real data and not too much empty cells to improve
performance. Not used row must be deleted to decrease memory usage. Modify
Documents and tests to met new feature. Testing time reduced in 80% after
deleted not used rows in document.

Conflicts:

	tests/Payroll/Test/PayrollValidatorTest.php
	tests/Payroll/repository/UPT ARAGUA -  BONO FIN DE AÑO 2013.xlsx