refactoring: cleanup our cookie handling, now the manager takes care of its own state. This solves some problems introduced by the use of the new HttpClient api (background: the httpContext is not thread save but we share the context between our threads)

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@9173 5f5364db-9458-4db8-a492-e30667be6df6
HttpWebConnection: use the same context, when calling SSLv3, thanks to Ronald for hinting.

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@9174 5f5364db-9458-4db8-a492-e30667be6df6
more GC friendly finalizer for the ImageInputStream

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@9175 5f5364db-9458-4db8-a492-e30667be6df6