Moira-python-client

Small refactor to satisfy users that use Python < 3.6

Make validation for Python-client like validation in Web Moira. It is need to make valiation right and unified for all Moira client sides.

[Use new validation for creating/updating triggers](https://github.com/moira-alert/python-moira-client/commit/3edb4c720d4b80ae8a4bd6117cb2b9cf0c5bec16)

[Return response object instead of string ID](https://github.com/moira-alert/python-moira-client/commit/5f2bccdd11d6ef6a2a548b9c7072037ebf0445c0)

‼️ Remove underscore-prefixed fields that contained scheduling time settings:

- `_start_hour`
- `_start_minute`
- `_end_hour`
- `_end_minute`
- `_timezone_offset`
- `disabled_days`

Because they were duplicates of data from sched field.

Please use sched field for scheduling settings instead.

- Fix missed disabled_days
- Push only tags create

- Add "/setMaintenance" methods 8
- Set login equal to auth_user by default if last one is specified 9
- Add "/config" methods 10
- Add support for changing moira notification state 16

- Added ability to subscribe for all triggers without specifying tags (moira-alert/moira236).