This weekend in PyObjC

I've made several pretty cool enhancements to PyObjC and py2app this weekend:

• There is now a fast path for the NSString/unicode bridge when Py_UNICODE_SIZE is 2. This is the default setting for Python.
• The default selector signature will have a void return value unless a "return" statement with an argument is used in the bytecode. In that case, it will default to an object return value.

This means that objc.accessor(...) isn't necessary for most setters!

• __bundle_hack__ is no longer necessary, py2app now sets a different environment variable to the current plugin during execution, and a hack is installed to NSBundle so that classes may respond to requests for their bundle with the +bundleForClass method. The class builder adds a default implementation of this to Python classes if this environment variable is set.
• Added objc.currentBundle(), which is equivalent to NSBundle.mainBundle() except after loading a plug-in. Makes it easier to load nib files.
• PyObjCTools.NibClassBuilder.extractClasses() now uses objc.currentBundle() instead of NSBundle.mainBundle(). This makes plugins less of a hassle to develop and allows identical code to be used for application or plugin development.
• objc.registerPlugin() and objc.pluginBundle() are now deprecated as they are no longer useful.

These all VASTLY improve support for plugins. Additionally, I have made some changes to the py2app bootstrap to support these new features, and I've cleaned it up so that it loads plugins into their own modules rather than stuffing them into __main__.

I have also started work on a new RemotePyInterpreter example, which runs the interpreter in a subprocess and communicates with it asynchronously. This will be useful for IDE work when it's done. The IPC protocol it uses is a cute little repr-based hack, loosely based on py.execnet. I'll also use this to implement out-of-process debugging (think pdb attach) and other fun things, hopefully in the near future.