Botbuilder-samples: Update es6 70.styling-webchat sample

[WashingtonKayaker]

the styling-webchat sample in javascript_es6 is out dated.

Description

I think that perhaps the entire javascript_es6 directory should be removed? If not, at least sample 70.styling-webchat is not longer applicable since the change to Direct Line impacts how secrets/tokens are used, This sample needs to be removed.

Note sure about sample 01.browser-echo.

[tdurnford]

@corinagum thoughts?

[mdrichardson]

01.browser-echo probably is one of the least popular samples, but it does demonstrate some interesting functionality: hosting the bot entirely in the user's browser.

[corinagum]

Agree with @mdrichardson :)

Not sure what you mean about sample 70... can't it just be updated? Web Chat samples already document this extensively.

[corinagum]

@axelsrz, FYI: I am removing labels since @WashingtonKayaker is part of the docs team.

[tdurnford]

The Web Chat samples request a token from Mock Bot to initiate the conversation, but 70.styling-webchat just uses a Web Chat secret. Neither are wrong, but I think we should encourage our users to use a token instead of their secret on their client sites.

[sgellock]

The web chat sample, if it needs updating, should be updated. I'm still of the opinion that the es_6 folder demonstrates concepts that have customer interest. @corinagum does Web Chat sample need an update?

[corinagum]

@sgellock, yes. Previously @compulim and I didn't make changes to Web Chat looking for the secret because of the ongoing secret/token discussion, but since it sounds like we are officially promoting token retrieval we can emulate this sample to look like Web Chat. I'm happy to make those edits. :)

[stevengum]

@sgellock and @corinagum I've labeled this for 4.6 and with a P2 label for now.

@corinagum I updated the title as well with where I _think_ we want to be, but can you determine if we want to keep sample 70 and update it, or if we want to remove it and update 01.browser-echo?

[corinagum]

~I think the plan is to update both. Updated title accordingly :)~

Updating this: I don't know why I thought 01.browser-echo needed to be updated. It does not. My PR will only update sample 70.