Add messageBack support to suggested actions

[corinagum]

Fix #1402

• DirectLineJS has been bumped with messageBack support
• Web Chat has been updated to allow messageBack suggested actions
• Integration tests for Mock Bot's suggested-actions command have been added
• image and title (what the button displays) are individually optional, but one or the other must be defined
• displayText represents the optional response from the user when a suggested action is selected
• text and value may be empty, in which case an empty suggested action is sent to the bot

Mock Bot with added suggested-actions

messageBack as JSON with display text.

[coveralls]

Pull Request Test Coverage Report for Build 760

• 12 of 20 (60.0%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+3.0%) to 48.428%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/component/src/Utils/AdaptiveCardBuilder.ts	0	3	0.0%
packages/component/src/Attachment/AdaptiveCardRenderer.js	0	5	0.0%

Totals
Change from base Build 749:	3.0%
Covered Lines:	786
Relevant Lines:	1466

---

💛 - Coveralls

[compulim]

Please rebase master. There are lot so changes around saga.

[corinagum]

@compulim @a-b-r-o-w-n I have pushed PR changes up. My tests pass locally, and I'm not sure why it's saying coverage went down since I added tests. I will check with @compulim in person to see if he has advice.

[corinagum]

@compulim and @a-b-r-o-w-n please ignore above comment - after a slight delay the travis build updated to say there was a 3% increase, and that tests are passing.