parameter validation

[smorken]

Add validation functions for the parameters passed into the CBM model functions. This is useful to catch errors early in simulations, rather than detecting errors later or at the end of long running simulations, which can be a huge time waster. It also is an opportunity to create useful error message feedback, rather than relegating this to lower level code which might not be as user friendly in this regard.

Things that can likely be pre-validated:

• parameter/variable shapes (for all parameters that are stored in numpy)
• parameter/variable value ranges
• invalid ids
• more complex relationships: for example check for missing yield curves,