added test provided for issue 596

provided by @chuck-jove on
https://github.com/propelorm/Propel/issues/596
order by alias is not supported in mssql. fixes #596 by @chuck-jove
fixed test
removed unused properties from OnDemandCollection which were never set.
added tests for PropelCollection new __clone() magic method
Merge pull request #609 from staabm/unused_properties

removed unused properties from OnDemandCollection which were never set.
fixed __clone() for PropelCollections containing scalar values
separate tests for __clone() using objects and scalars
expect PropelException when cloning PropelOnDemandCollection's
Merge pull request #610 from staabm/clone_test

added tests for PropelCollection new __clone() magic method
added failing testcase for issue #608
allow withColumn() and select() again. fixes #608.
Merge pull request #611 from staabm/issue608

select() + withColumn() query error
Merge pull request #607 from staabm/issue596

added test & fix provided for issue 596
Merge remote-tracking branch 'upstream/master'