contrib/jwrapper: Retrieves existing extern classes using grep

Signed-off-by: Frédéric Vachon <fredvac@gmail.com>
contrib/jwrapper: Added basic UI

Signed-off-by: Frédéric Vachon <fredvac@gmail.com>
contrib/jwrapper: Added README

Signed-off-by: Frédéric Vachon <fredvac@gmail.com>