Support "FEDERATED" repository types

[RoeeDr]

Currently, calling get_repositories on artifactory that contains federated repositories will crash:

Traceback (most recent call last):
  File "/venv/lib/python3.9/site-packages/artifactory.py", line 2137, in get_repositories
    return self._get_all(
  File "/venv/lib/python3.9/site-packages/artifactory.py", line 2109, in _get_all
    item.read()
AttributeError: 'NoneType' object has no attribute 'read'

This happens since create_by_type doesn't support the federated type and just returns None.

I can also open a PR on it myself, since the federated type should mostly be handled like a local repository if I understand correctly from the docs:
https://www.jfrog.com/confluence/display/JFROG/Federated+Repositories

[beliaev-maksim]

looks like it is similar to local + additional features

I think we need to create a new type and for the moment just inherit the functionality of local one.

please submit a PR with proposal

[RoeeDr]

@beliaev-maksim do you have any estimate on when can you review the PR? No rush on anything, just want to get an estimate on the fix on my end (tested the code on real federated repos btw)