Remove Jigsaw dependent code

[vivien]

Find another way to know unicorn_home parameter (currently by a jvm parameter), whether programatically, or with web.xml

[tgambet]

I removed libraries that were needed only for Jigsaw. There is not really any Jigsaw dependent code, but now that we chose not to support Jigsaw anymore we'll be able to use more methods of the servlet api, like, amongst other, methods to get the path of the application (and get rid of the jvm parameter), methods to get the url where unicorn is deployed (get ride of UNICORN_URL in the conf file), and methods to forward requests between servlet or to send redirects to the user. None of these is needed for milestone 1.0.

[jean-gui]

"get ride of UNICORN_URL in the conf file" I am not sure we should do that as we can use proxies that change URLs. Or, by default Unicorn should try to guess its URL, but if UNICORN_URL is present, then the latter should be used.

[tgambet]

Done, unicorn.home is now guessed by unicorn during initialization. Note that unicorn must be deployed by the servlet server and not run directly from the war in order to work properly.