--2a format still claims Development format for its format description

[John A Meinel]

It seems that RepositoryFormat2a inherits from RepositoryFormatCHK2 (--dev6-rich-root) but doesn't provide a new "get_format_description"

Which means that both "bzr info -v" and Launchpad cannot tell a --dev6 repo from a --2a one... :(

Should be simple enough to fix
We just need to add something like:
def get_format_description(self):
    """See RepositoryFormat.get_format_description()."""
    return ("Development repository format - rich roots, group compression"
        " and chk inventories")