more differentiated exceptions

[Jaymon]

Right now everything just gets raised as an InterfaceError, but this should be broken down even more, so there should be IntegrityError and ConnectionError etc. all children of InterfaceError, this way we can normalize the errors between all interfaces and yet be able to pick and choose what we want to catch because right now if you just want to ignore an integrity error you have to catch all the errors which is pretty bad, because the code might silently ignore a more serious error