Refactoring: replace data value path_info by classes

[dmpetrov]

Manipilating with data values does not seem like a good practice:

self.path_info = {"scheme": "hdfs", "user": self.user}

It can be replaced by classes:

class BasePathInfo(object):
    def __init__(self, path=None):
    ....

class HdfsPathInfo(BasePathInfo):
    def __init__(self, path=None):
    ....

etc...

[efiop]

For the record: this got a lot worse since dir logic generalization, so we are prioritizing it to start using something like suggested PathInfo, which, when casted to string, would result in url for non-local paths and relpath for local paths.