allClassTestsInOneFile.scala script

Added new allClassTestsInOneFile.scala script.  The script will automatically generate specs2-class.jar by compile and package classes defined in specs-class.scala.  Abstract class is used to to defined SpecificationClass in specs2-class currently, to make it concrete class, you will need to uncomment the 'def is' and add 'override' to 'def is' in iSpecification template in allClassTestsInOneFile.scala script.