docs: add documentation for dbus methods
docs: add documentation for dbus methods

Add methods Info, Mark and GetSlotStatus

Signed-off-by: Jan Remmet <9c9945a0da87ab3eec6bcf12544e291bfd78ecfe@phytec.de>

jluebbe/rauc,jluebbe/rauc,rauc/rauc,ejoerns/rauc,ejoerns/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc,rauc/rauc