Tasks for v1

[anandtrex]

• Return Error instead of warning when keys are not returned. (Because None has the same behaviour as False)
• In the __setattr__ and dict conversion functions ensure that _INSTANCE_VAR_LIST is checked
• remember to disallow any names that are not valid variable names (str.isidentifier())
• remember to disallow any names starting with an underscore.
• Create a __dir__ method that returns the keys in the dictionary for autocomplete
• Add all the functions to _INSTANCE_VAR_LIST
• Ensure that one can create sub-directories on the fly
• Remove complicated logic from __getattr__ as this is only called as a last resort if nothing is found.
• Don't remove __getstate__ handling because this is a possibility that it doesn't exist
• Why are we using the descriptor protocol (i.e. __set__ ?)
• Make sdictm an instance of MutableMapping and sdict an instance of ImmutableMapping. Allows for better type checking
• Handle _ipython_canary_method_should_not_exist_. See ipython code