Appy 0.6.4

appy.pod
* Added Renderer param "overwriteExisting" allowing to overwrite existing POD result instead of raising an exception (defaults to False)

appy.gen
* bugfix in Date intervals coming from search.pt.
* implemented ToolMixin.performLogin (inspired from Plone authentication)
* minor bugfix while redirecting user to a page that must display a global status message
* logged every translation deletion.
* when redisplaying the 'edit' view, empty any password field.
* added the possibility to freeze, within Pod fields, documents that are normally generated with appy.pod.
* Minor changes in the test system
* XmlUnmarshaller can unmarshall XML content from a string, file handler of file path
* any Appy object now has a method 'getField(name)' that returns a given field (=Appy type)
* bugfix while counting number of tests found in a gen-application.
* bugfix while indexing empty string values: bugfix while accessing object from a query without security enabled.