decorator logging

[lukesmurray]

We currently use @Property and @var.setter to set and get things on the engine/models.

We want to wrap these so that the @Property logs the current value and @var.setter logs var's previous value and var's new value

[soyapark]

this feature is an essential part of #87

[soyapark]

Can we make some progress for this feature (#87)? As we have seen from our deployment, we need more affordance for debugging and line-by-line debugging seems like a good way to pursue

[lukesmurray]

will work on this today

[lukesmurray]

in progress on #175