Teams notifications

[domwhewell]

Issue
#127

Description of the Change
This PR adds support for teams notifications

• A new NotificationsCenter class has been added (notifications_all.py) which routes notifications based on whats enabled (Can be to both Slack and Teams)
  • This new class has only slight variations on the current SlackNotifications class
• The Slack Configuration model has been changed to a Notifications Configuration model which will hold all the configuration for all avaliable notification types (currently only slack and teams)

I have changed the Review Configuration and the admin page to reflect the ability to enable and configure both teams and slack.
The oplog and background tasks have all been updated to use the new NotificationCenter to send a notification. which is then routed based on what is enabled

Alternate Designs
I think this is the most efficient design rather than having a new Configuration model for each notification service

Possible Drawbacks
None but Microsoft teams has a per channel webhook unlike slack so this does not give teams the ability to post to a specific project teams channel

Verification Process
Have created tests for the new models, and have also used both a teams and slack webhook to send notifications

Release Notes
Added support for microsoft teams in a new "Notifications Configuration" under command center