Return a new URLFactory in function of the URL type.
an URL pointing to a jar file will return a JarURLFactory
and an URL pointing to a directory file will return a DirURLFactory.
Parameters: url - the base URL a new URLFactory in function of the URL type. throws: IOException - when cannot find a specialized factory for the given URL.
Returns a new URL basically adding path to the base URL.
Parameters: path - the path to add to the URL. a new URL. throws: IOException - when created URL is invalid.