Add RemoteFileSigLevel to available pacman options

Signed-off-by: Tasos Latsas <tlatsas@gmx.com>
Signed-off-by: Rémy Oudompheng <remy@archlinux.org>
pycman: support IgnorePkg and similar options in init_with_config.
pycman: UseDelta option can also take a value (FS#34791)