initial lrwp: cacti_device, cacti_graph with :create action

initial lrwp support. please drop comments what you think and if i should refactor it somehow differently

currently only create is supported, if graph or device already exists, it will just not mark resource "updated"
delete does not exist, because there's no cli tool for that in cacti itself (for now)

for me it bothers the shellout calls, i'm not certain it's the best way and that values would be properly escaped for shell