Category on NSException to easily define name/reason for exceptions and reference by enum type
and more stuff
still need another commit
Added const struct arrays to define the expected structure of a returned fixture data set (better testing)
Refactored to now use the term UserData instead of Fixture

The term fixture is more relevant later when implementing the
CustomUserData variation. But even then the correct logic is that
instances of "CustomUserData" represent test fixtures. It's quite
feasable that the class is being used in a way that's got nothing to do
with testing.
JALUserDataDictionarySpec & Tests

The user data structs together with accessors have been abstracted out
into a new clas and tests written. Just need to finish implementing it
and write some more tests.
That's it for today - working on JALUserDataDictionarySpecTests

Only need to add tests for classname retrieval now, which are probably
(almost) identical. And then I can get back onto the default user data
class. Testing it will require init with a
JALUserDataDictionarySpecMock!