Add a method (empty) for preSolve called checkRestrictions that can b…

[pkofod]

…e overwritten in classes inheriting from AgentType to check for illegal parameter values.

Fixes #204 by providing infrastructure for checking parameter restrictions.

This way of calling AgentType.preSolve(self) should be fine right @mnwhite ? Currently, all the classes that defined a preSolve failed to check for length time varying things for example, unless AgentType.preSolve was called somewhere I cannot see. The idea is basically that if you have any important restrictions such as values of CRRA, DiscFac, or something else, you write your own checkRestrictions method and raise an exception if the input fails to meet the requirements.

This way still allow users to construct the models, checkRestrictions is simply guarding calls to solve().

[pkofod]

Would you look at that. I caught a mistake thanks to the initialization tests :) (I forgot to import AgentType)

[llorracc]

@pkofod Thanks for adding this. But it looks like you changed two things at once: Both this and the PR that I just merged modified the same place in IndShockConsumerType, so it is giving a "conflict" error.

If you could resolve the conflicts and let me know, I will merge.

[pkofod]

If you could resolve the conflicts and let me know, I will merge.

Ah yes, that happens. I'll resolve the conflicts!

[shaunagm]

Can you add a release note, @pkofod?