simcf Input Checks and Error Messages

[chrisadolph]

simcf presently does little to check for acceptable inputs, and (mostly as a result) gives nonsensical error messages.

Checks need to happen at least in two ways: checks for cf objects, to make sure inputs are feasible for construction or editing of cf objects, and checks for inputs to simulation functions.

We never want to accidentally exclude inputs that would work, so if you're unsure if something is an error (just unwise), use warning() instead of error().

[csjohns]

For the record, this issue is being dealt with simultaneously with modularity, by building a new central simcf() which includes a range of input checks while converting inputs to cf objects to standardize process. Code to follow in a bit.