Napalm-iosxr

For information regarding the release visit:

https://github.com/napalm-automation/napalm-iosxr/milestone/3?closed=1

Bugfix:
- 20 Fixed typo in requirements file

New Methods:
- 10 `get_users()`
- 8 `get_ntp_peers()`
- 6 `traceroute()`
- 1 `get_probes_config()` and `get_probes_results()`

Templates:
- 4 templates for SLA probes

Changes:
- As per napalm-automation/napalm-base12 - Rename the method `get_ntp_peers` to `get_ntp_stats` and slightly change the output. Check the PR for more details

Driver can now be discovered by napalm-base.

First standalone version. Same features as napalm-0.60.0.