Core shouldn't have to know about the clients in advance

[jumentous]

So, #1971, #1972, #1973 are bugs that were discovered in the trying to fix this point.

I am looking at adding a new UI to deluge, and in the process noticed that the core currently matches the chosen UI and launches the appropriate client. This makes it impossible to add a client developed out of the deluge tree.

This patch modifies setup to export the UI classes as entry points and load the entry point for the class. Details for this method can be found here:  http://aroberge.blogspot.com/2008/12/plugins-part-6-setuptools-based.html and  http://peak.telecommunity.com/DevCenter/PkgResources#locating-plugins

Note that it doesn't actually do a find_plugins yet, it's just moving towards it.

Now i realize that there is already a plugin format for deluge however i thought this more appropriate for something that will be relatively static and can be deployed by rpm/deb.

Obviously, comments/revisions are encouraged.

[jumentous]

I've put the branch on github for the patches #1971 #1972 #1973 and this under detach-ui

 https://github.com/jamielennox/deluge/tree/detach-ui