[blameable] Support for many-to-one association with XML mapping
Merge pull request #777 from CharlyP/xml-many-to-one-management

[blameable] Support for many-to-one association with XML mapping
modified Timestampable and Blameable behaviors to accept an array of tracked fields
added attribute checking to the new many-to-one part of the Blameable XML driver
Merge branch 'timestampable-field-array' of github.com:smatyas/DoctrineExtensions into timestampable-field-array

Conflicts:
	doc/blameable.md
	lib/Gedmo/Blameable/Mapping/Driver/Xml.php