app: fix markets view layout issues

[buck54321]

Fixes issues where overflow and div sizing were acting weird on resize.

Creates and uses a stylish scrollbar class. Enables manual chart div click-drag resizing and remembers the user's preference across sessions.

Also corrects a recent regression where certain order form elements were not being hidden for market orders.

Most of the loc are just html indentation changes. Best tested with the test app server.

resolves #550, #514, #296, #539

[buck54321]

739d61e contains fixes for #516 and #532. Sorry if anybody was mid-review.

[chappjc]

When starting dexc with already configured wallets (everything rebuild and hard-refreshed and cache disabled):

After unlocking in the /wallets page, the markets view is fixed:

Separately after resolving the above with an unlock, I think this came after a trade:

[buck54321]

@chappjc, I was unable to reproduce the formatCoinValue error. I've added a console error message that should give some insight if you can still reproduce.

[chappjc]

I'm not seeing it any more either, at least not with a fresh harness. The one I had with over 1 million DCR was pretty unusual.

[chappjc]

Here's the repro with 1218684.00822222:

function str(x){
  return x.toLocaleString('en-us', fullPrecisionSpecs);
}

const fullPrecisionSpecs = {
  minimumSignificantDigits: 4,
  maximumSignificantDigits: 8,
  minimumFractionDigits: 8,
  maximumFractionDigits: 8
}
let v = 1218684.00822222
var vStr = str(v)
console.log(vStr)
var [whole, frac] = vStr.split('.')
console.log(whole, frac);

https://jsbin.com/daqukodoqo/edit?js,console

I think toLocaleString should always output at least 2 fraction digits.

[buck54321]

Fixed formatCoinValue in 741523f. We could use unit tests for functions like this, so I actually tested a couple of js unit testing frameworks, but ran into some unfortunate issues with both. I'll keep looking for a suitable framework.