Make it possible to create a user via API

When POSTing to the /users URL, wrap data within an extra hash. This is per the
API document.

    $ python -m unittest tests.foreman.api.test_user
    ....s......s......s.....s......s......s.
    ----------------------------------------------------------------------
    Ran 40 tests in 79.635s

    OK (skipped=6)

Targets #1578.
Merge pull request #1585 from Ichimonji10/create-user

Make it possible to create a user via API
Make Sphinx happy

Do not attempt to auto-generate API docs for the non-existent
`robottelo.api.apicrud` module. Fix a module reference.
Skip known-failing tests

Skip tests that are known to fail due to BZ 1154156.

    $ nosetests tests/foreman/api/test_multiple_paths.py -m _Host
    ..S.S.....S.....SSSS
    ----------------------------------------------------------------------
    Ran 20 tests in 48.694s

    OK (SKIP=7)

Make method `Host.create` subnet a nested hash of parameters, e.g. `{'host':
{...}}`.
Merge pull request #1586 from Ichimonji10/docs

Make Sphinx happy
Merge pull request #1588 from Ichimonji10/create-host

Skip known-failing tests
Make API logging more useful

Make the API client log out a warning whenever an HTTP 4XX or 5XX response is
received. Demote messages detailing the contents of every single request and
response from priority "info" to "debug".
Merge pull request #1589 from Ichimonji10/better-logging

Make API logging more useful
Trim down .gitignore file

Only ignore files and directories that are relevant to this project.
Unnecessarily ignoring files can make troubleshooting especially hard in
situations where a troublesome file is invisible to git.
Merge pull request #1587 from Ichimonji10/gitignore

Trim down .gitignore file
Repositories to handle new checksum-type attribute.

Updated locators, factory, repository modules for the support.
Updated the CRUD functions for the support.

Also added two new tests `test_create_repo_5` and
`test_positive_update_3` to the `ui/test_repository` module.