Python-application

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* Fixed syslog on platforms that do not support it
* Added outgoing_ip_for method to host object

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* Added NullType in order to allow Null to be pickled
* Made NullType a singleton to prevent multiple instances when unpickling

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* Improved memory_dump's output using console size information
* Added support for detecting object cycles in application.debug.memory

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* Made Null from application.python.util an instance. See NEWS.
* Improved processing speed for post_notification.

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* Added the missing application.log package to the build

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* Depend on python2.5 or newer
* Modified Null not to return self for __setattr__ and __delattr__
* Added indexing support for the Null class
* Allow a Null object to be a descriptor
* Added __len__ method to the Null class
* Added iteration support for the Null class
* Added __contains__ method to the Null class
* Added context management support to the Null class
* Added discard_observer method to NotificationCenter
* Added comment to clarify behaviour
* Fixed threading issues with adding and removing observers
* Fixed handling of settings which contain uppercase characters and dashes
* Added support for weakly referencing observers in the notification system
* Added example of how to have a weakly referenced notification observer
* Removed deprecated functionality
* Added purge_observer method on NotificationCenter
* Added dynamic host properties to application.system
* Removed resolution test from Hostname configuration data type
* Improved error message for invalid type in IPAddress
* Removed twisted logging backend and added a logging extension for twisted
* Improved logging functions and added some commonly used aliases
* Fixed initial setting of the current log level