CIF controller properties checker: warn if input model doesn't have input variables

If the model doesn't have input variables, it is likely lacking the hardware mapping. This means it probably won't produce proper bounds for bounded response, but instead indicates there are cycles, etc. Noting this early on with a warning helps users, especially if checks take a long time. Also, it helps to point at the cause in the model that may be causes that some checks don't hold.

Addresses #892