Mark private Whim::Core attributes

[adherzog]

Continuing conversation from PR #44:

It seems a bit weird the way author_photo_directory will attempt to create the directory, which will probably happen when you call $self->author_photo_directory->mkpath in _make_homedir. Is the intention that a user might want to set author_photo_directory to a path separate from the default in the whim home directory? If so, I'd handle it the same way home is handled - a required, non-lazy attribute with it's own trigger.

No, I don't intend that people would set these sub-directories separately. I've simplified the checks for them accordingly.

You might consider renaming those attributes to start with an underscore, just to make it clear which attributes are for internal use and which are available to pass to the constructor and/or access from outside of the module. From what I can tell, author_photo_directory isn't used from anywhere outside of Whim::Core.