Support for multiple notifications on page

[evgenyboxer]

What current issue(s) from Trello/Github does this address?
Precursor for the connectivity branch. I needed a way to show multiple notifications on page.

What problem does this PR solve?
Being able to show multiple notifications on page. So for example, you could see a wallet upgrade warning notification, and other notifications (such as the errors/info/etc)

How did you solve this problem?
I have used React Notification System, which is a pretty solid library. I have implemented a light wrapper for it.

How did you make sure your solution works?
Extensive QA

Are there any special changes in the code that we should be aware of?

Is there anything else we should know?

• Unit tests written?
  Yes.

[coveralls]

Coverage increased (+0.2%) to 47.002% when pulling 20346bb on rework-notification-system-2 into 2c7c83f on dev.

[coveralls]

Coverage increased (+0.2%) to 47.002% when pulling 20346bb on rework-notification-system-2 into 2c7c83f on dev.

[coveralls]

Coverage increased (+0.2%) to 47.002% when pulling a510d68 on rework-notification-system-2 into 2c7c83f on dev.

[coveralls]

Coverage increased (+0.2%) to 47.002% when pulling 299a84b on rework-notification-system-2 into 2c7c83f on dev.