Refactored the Context.currentLanguage out of a thread-local #1711

As that was making the CCL leak.
Javac: disabled the shared zip cache #1711

It was leaking jars and required a manual cache reset. About time I disabled it.
Launcher: do not make the CCL static anymore #1711

It was causing leaks, and it would not work when invoked twice with different
sysrep anyways.
CeylonCompileTool: temporary? workaround for #1663

Still needs test
CeylonClassLoader: added method to clear its URL leak #1711
cosmetic: imports cleanup
CeylonClassLoader: made it possible to instantiate with a given class path and check if the class path is still valid #1711
Ant tasks: cache the class loader in a project reference #1711

And clean it up on build finish
Launcher: try to reset the LogManager to clear the LogManager$Cleaner that leaks the CCL #1711
Added disabled test for #1711 for when we come back to the problem