changed the conditions whether updating references can be enabled or not for rename refactoring except Rename Local Variable (Issue #81)

* the target element should has the enclosing type
* the type is PSR-0 compliant if the type is in the namespace
* the type name equals the file name if the type is not in the namespace (Issue #72)
changed the PDTModelUtils class to use BACK_SLASH constants instead of backslashes
added the PHPType class that provides information about the type as a PHP class, interface, trait, and namespace
improved the PHPType#inNamespace() method
changed the PHPRenameProcessor class to use a PHPType object instead of the PDTModelUtils class
removed unused methods from the PDTModelUtils class
added the methods equals(IType), equals(Object), equals(String) to the PHPType class
changed the PDTModelUtils#isInstanceOf(IType, String) method to use the PHPType#equals() method instead of the PDTModelUtils#isSameType() method
removed the methods PDTModelUtils#isSameType(IType, IType) and isSameType(IType, String)
added the methods isInstanceOf(IType), isInstanceOf(String) to the PHPType class
changed the classes RenameFieldProcessor, RenameMethodProcessor, RenameTypeProcessor to use the PHPType#isInstanceOf() method instead of the PDTModelUtils#isInstanceOf() method
removed the methods PDTModelUtils#isInstanceOf(IType, IType) and isInstanceOf(IType, String)
fixed a defect that caused references not to be sometimes updated when renaming a field (Issue #80)
added the PHPMethod class that provides information about the method as a PHP method or function
changed the RenamePHPElementAction class to use the PHPMethod#getFarthestOverriddenMethod() method instead of the RenamePHPElementAction#getFarthestOverriddenMethod() method
removed the getOverriddenMethod() method and the OverriddenMethodFinder class from the PDTModelUtils class