Fixes #21179 - Upgrade to enzyme@3.0.0

Enzyme needs to be upgraded to support react@16. In upgrading I
found that using jest's snapshot feature would greatly improve
several of the tests that were in place. I've changed these
tests to use snapshots and added enzyme-to-json to support...

Fixes #18957,#18193,#18678,#18853 - notifications redux

Refactored notifications to work with redux, fixed
several UI related bugs, added tests.
flux is now unused, this is based on @gailsteiger's
previous work.