Fix issue #697

Fix a problem in parsing xml configuration file.
Adjust Propel Configuration TreeBuilder to correctly parse associative arrays.
Adjust XmlToArray class to correctly convert numeric values.
This commit fixes #697
Merge pull request #717 from cristianoc72/xml-issue

Fix issue #697
Propel2-710 Propel compatibility with Symfony 2.5 components

replaced deprecated validator class with new recursive one introduced in symfony 2.5
in order to make propel2 usable with symfony 2.5

fixes #710
replaced BufferedOutput with StreamOutput class which is available since SF 2.3

added check for LegacyValidator class in order to load the correct Validator classes below SF 2.5 and from 2.5

changed requirements for SF libraries from 2.3 up to 2.5>=2.3,<2.6